Lecture 2 - Identification of Transistor Amplifier Circuits PDF

Lecture No. 2: Identification of Transistor Amplifier Circuits ECE21115: Electronic Circuits Analysis and Design, Lecture UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONI...

Lecture No. 2: Identification of Transistor Amplifier Circuits ECE21115: Electronic Circuits Analysis and Design, Lecture UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering Lecture No. 2: Identification of Transistor Amplifier Circuits Multi-transistor Configuration Lecture No. 2: Identification of Transistor Amplifier Circuits UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 3 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair A Darlington transistor configuration 𝐼𝐶 (or simply the Darlington pair) consists of two BJT transistors, wherein the emitter of one transistor is connected to the base of the other 𝐼𝐵 𝛽1 transistor, resulting to a very high current gain 𝛽2 These two transistors will act as one to produce a “superbeta” transistor. 𝐼𝐸 The typical beta of Darlington pair is more than 1000. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 4 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair – Key Features High Current Gain – The 𝐼𝐶 current gain (β) of a Darlington pair is the product of the 𝐼𝐵 𝛽1 current gains of the two transistors. 𝛽2 𝐼𝐸 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 5 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair – Key Features Low Input Current – The 𝐼𝐶 configuration requires very little input current to control a large 𝐼𝐵 𝛽1 output current, making it useful in applications where power 𝛽2 needs to be amplified. 𝐼𝐸 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 6 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair – Key Features Saturation Voltage – One 𝐼𝐶 downside is that the Darlington pair has a higher saturation 𝐼𝐵 voltage (typically around 1-2V), 𝛽1 as the voltage drop is the sum of the base-emitter drops of the 𝛽2 two transistors (about 0.7V 𝐼𝐸 each). UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 7 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair The emitter of the first transistor is 𝐼𝐶 connected to the base of the second transistor. Both collectors 𝐼𝐵 are tied together, and the final 𝛽1 output is taken from the emitter of 𝛽2 the second transistor. Hence, similar to the configuration of an 𝐼𝐸 emitter follower transistor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 8 Lecture No. 2: Identification of Transistor Amplifier Circuits The Darlington Pair - Applications Power Amplifiers –often used in 𝐼𝐶 power amplification circuits, such as motor drivers, audio amplifiers, 𝐼𝐵 and relay drivers. 𝛽1 Switching Applications –used in 𝛽2 switching applications where a small base current is needed to 𝐼𝐸 switch on a larger load. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 9 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) The complementary feedback pair 𝐼𝐶 (a.k.a. Sziklai pair) is another type of multi-transistor configuration. 𝐼𝐶1 = 𝐼𝐵2 𝛽2 Instead of using two NPNs, the feedback pair utilizes one NPN and 𝐼𝐵 one PNP as shown in the figure. + 𝛽1 𝐼𝐶2 𝑉 The NPN’s collector is connected to 𝐵𝐸1 𝐼𝐸1 − the PNP’s base. The NPN’s emitter and PNP’s 𝐼𝐸 collector are tied together. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 10 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) High Current Gain – Like the 𝐼𝐶 Darlington pair, the Sziklai pair 𝐼𝐶1 = 𝐼𝐵2 achieves high current gain by 𝛽2 using two transistors in tandem. 𝐼𝐵 𝐼𝐶2 The gain is approximately the + 𝑉𝐵𝐸1 𝛽1 product of the gains of the − 𝐼𝐸1 individual transistors, similar to 𝐼𝐸 a Darlington pair. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 11 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) Lower Saturation Voltage – 𝐼𝐶 One of the major advantages of 𝐼𝐶1 = 𝐼𝐵2 the Sziklai pair is its lower 𝛽2 saturation voltage. While the 𝐼𝐵 𝐼𝐶2 Darlington pair typically has a + 𝑉𝐵𝐸1 𝛽1 saturation voltage of 1.2-2V, the − 𝐼𝐸1 Sziklai pair's saturation voltage 𝐼𝐸 is closer to 0.2-0.3V. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 12 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) Complementary Transistors – 𝐼𝐶 The Sziklai pair uses one NPN 𝐼𝐶1 = 𝐼𝐵2 𝛽2 and one PNP transistor (or vice versa), unlike the Darlington 𝐼𝐵 + 𝛽1 𝐼𝐶2 pair, which uses two transistors 𝑉𝐵𝐸1 − 𝐼𝐸1 of the same type. 𝐼𝐸 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 13 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) Feedback for Stability – The 𝐼𝐶 feedback loop created by the 𝐼𝐶1 = 𝐼𝐵2 𝛽2 complementary transistors helps stabilize the pair and 𝐼𝐵 + 𝛽1 𝐼𝐶2 reduce distortion, making it 𝑉𝐵𝐸1 − 𝐼𝐸1 suitable for applications such as 𝐼𝐸 audio amplifiers. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 14 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) First Transistor – The emitter of 𝐼𝐶 the first transistor is connected to the base of the second transistor. 𝐼𝐶1 = 𝐼𝐵2 𝛽2 Feedback – The base of the first 𝐼𝐵 transistor is connected to the + 𝛽1 𝐼𝐶2 𝑉 collector of the second transistor, − 𝐵𝐸1 𝐼𝐸1 creating a feedback loop that 𝐼𝐸 helps control the overall gain. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 15 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) Audio Amplifiers – The Sziklai 𝐼𝐶 pair is often used in audio 𝐼𝐶1 = 𝐼𝐵2 𝛽2 power amplifiers, where its lower saturation voltage and 𝐼𝐵 + 𝛽1 𝐼𝐶2 high current gain are 𝑉𝐵𝐸1 − 𝐼𝐸1 advantageous for delivering 𝐼𝐸 cleaner sound. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 16 Lecture No. 2: Identification of Transistor Amplifier Circuits The Complementary Feedback Pair (Sziklai Pair) Switching Applications – Like the 𝐼𝐶 Darlington pair, the Sziklai pair is also used in switching circuits 𝐼𝐶1 = 𝐼𝐵2 𝛽2 where small base currents need to 𝐼𝐵 control larger loads. + 𝛽1 𝐼𝐶2 𝑉 Voltage Regulators – Its low 𝐵𝐸1 𝐼𝐸1 − dropout voltage makes it useful in 𝐼𝐸 voltage regulation circuits. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 17 Lecture No. 2: Identification of Transistor Amplifier Circuits Comparison of CFP and DP Lower Saturation Voltage – The Sziklai pair has a lower voltage drop in the "on" state, which makes it more efficient in some power applications. Similar Current Gain – Both configurations offer high current gain, but the Sziklai pair achieves it with complementary transistors. Response Time – The Sziklai pair generally has a faster response time compared to the Darlington pair, making it suitable for high-speed switching applications. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 18 Lecture No. 2: Identification of Transistor Amplifier Circuits Multi-transistor Configuration The multi-transistor configuration presented 𝐼𝐶 𝐼𝐶 possess very high values of 𝛽. 𝐼𝐶2 𝐼𝐶1 = 𝐼𝐵2 𝐼𝐶1 𝛽2 These transistor 𝐼𝐵 configurations are 𝛽1 𝐼𝐵 mainly used as current + 𝑉𝐵𝐸1 𝐼𝐸1 = 𝐼𝐵2 + 𝛽1 𝐼𝐶2 amplifiers. − 𝛽2 𝑉𝐵𝐸1 𝐼𝐸1 + − These transistor 𝑉𝐵𝐸2 configurations will be − 𝐼𝐸 𝐼𝐸 seen in our future topic, the power amplifier. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 19 Lecture No. 2: Identification of Transistor Amplifier Circuits Transistor Cascoding Transistor cascoding is usually implemented to improve an amplifier’s output impedance. Based on the derived voltage gain equations from the previous module: the higher the output impedance, the higher the gain is. 𝑟𝑜 ||𝑅𝐶 𝑍𝑂 𝐴𝑉(𝐵𝐽𝑇,𝐶𝐸) = − = − 𝑟𝑒 𝑟𝑒 𝐴𝑉(𝐽𝐹𝐸𝑇,𝐶𝑆) = −𝑔𝑚 ⋅ (𝑟𝑜 | 𝑅𝐷 = −𝑔𝑚 ⋅ 𝑍𝑂 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 20 Lecture No. 2: Identification of Transistor Amplifier Circuits Transistor Cascoding (BJT) Cascoding is done by +𝑉𝐶𝐶 connecting two transistors in “series” as shown in the 𝑅𝐶 figure. 𝑉𝑂𝑈𝑇 𝑉𝐵𝐼𝐴𝑆 The stages are in 𝑄1 a cascode configuration stacked in series, as opposed 𝑅𝐵 to cascaded for a standard 𝑉𝐵𝐵 + 𝑉𝐼𝑁 𝑄2 amplifier chain. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 21 Lecture No. 2: Identification of Transistor Amplifier Circuits Transistor Cascoding (JFET) +𝑉𝐷𝐷 Similar principle with the BJT was followed to construct a 𝑅𝐷 common source cascode 𝑉𝑂𝑈𝑇 amplifier. 𝐽1 The lower transistor is known as the amplifying transistor and is configured as common source −𝑉 𝐺𝐺 + 𝑉𝐼𝑁 𝐽2 circuit. The upper transistor is the cascode transistor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 22 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit A current mirror circuit is an analog circuit designed to copy (or "mirror") the current flowing 𝐼𝑅𝐸𝐹 through one active device (typically a transistor) into another. 2𝐼𝐵 𝐼𝐶 𝐼𝐶 The main goal of a current mirror circuit is to make a perfect copy of 𝐼𝐵 𝐼𝐵 the reference current, 𝐼𝑅𝐸𝐹. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 23 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit A current mirror circuit is an analog circuit designed to copy (or "mirror") the current flowing through one active 𝐼𝑅𝐸𝐹 device (typically a transistor) into another. 𝐼𝐶 2𝐼𝐵 The main goal of a current mirror circuit 𝐼𝐶 is to make a perfect copy of the reference current, 𝐼𝑅𝐸𝐹 , by maintaining 𝐼𝐵 𝐼𝐵 the same current in the output device as in the reference device, regardless of changes in load or supply voltage. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 24 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit – Key Features Constant Current Source – it effectively acts as a constant current source, providing a stable current 𝐼𝑅𝐸𝐹 output. 𝐼𝐶 Simple Design – the basic current 𝐼𝐶 2𝐼𝐵 mirror circuit typically uses two transistors (BJTs or MOSFETs), 𝐼𝐵 𝐼𝐵 where the current through the first (reference) transistor is mirrored in the second (output) transistor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 25 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit – Key Features Proportionality – in more advanced designs, the current in the output branch can be scaled proportionally 𝐼𝑅𝐸𝐹 to the reference current by adjusting the transistor sizes or 2𝐼𝐵 𝐼𝐶 resistor values. 𝐼𝐶 𝐼𝐵 𝐼𝐵 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 26 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit The circuit is called a current mirror because it replicates or mirrors the current from one 𝐼𝑅𝐸𝐹 transistor to another. Essentially, the input current (reference 2𝐼𝐵 𝐼𝐶 current) is reflected in the output, 𝐼𝐶 maintaining the same or a 𝐼𝐵 𝐼𝐵 proportionally scaled current in the output branch. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 27 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit Applications Analog Integrated Circuits – current mirrors are commonly used in analog ICs as biasing elements, where a 𝐼𝑅𝐸𝐹 stable reference current needs to be distributed across different parts of 𝐼𝐶 2𝐼𝐵 the circuit. 𝐼𝐶 Amplifiers – they are also used in 𝐼𝐵 𝐼𝐵 differential amplifiers and operational amplifiers, where a constant current is necessary for proper operation. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 28 Lecture No. 2: Identification of Transistor Amplifier Circuits The Current Mirror Circuit Applications Active Loads – current mirrors can be used as active loads to improve the gain of amplifier stages by providing a high- 𝐼𝑅𝐸𝐹 impedance load. Current Sources/Sinks – in applications 𝐼𝐶 2𝐼𝐵 where a precise current needs to be 𝐼𝐶 supplied to a load (such as in voltage regulators or analog-to-digital 𝐼𝐵 𝐼𝐵 converters), current mirrors are an ideal solution. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 29 Lecture No. 2: Identification of Transistor Amplifier Circuits Types of Current Mirrors Basic Current Mirror – Uses two identical transistors and mirrors the current exactly. 𝐼𝑅𝐸𝐹 Wilson Current Mirror – An 𝐼𝐶 improved version that provides 𝐼𝐶 2𝐼𝐵 better accuracy and higher output resistance, reducing the effect of 𝐼𝐵 𝐼𝐵 variations in transistor properties. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 30 Lecture No. 2: Identification of Transistor Amplifier Circuits Types of Current Mirrors Cascode Current Mirror – Provides high output impedance and improved voltage regulation. 𝐼𝑅𝐸𝐹 Widlar Current Mirror – Allows 𝐼𝐶 for scaling of currents without 𝐼𝐶 2𝐼𝐵 requiring large resistors or components. 𝐼𝐵 𝐼𝐵 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering Lecture No. 2: Identification of Transistor Amplifier Circuits Differential Amplifier and Operational Amplifier Circuits Lecture No. 2: Identification of Transistor Amplifier Circuits UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 32 Lecture No. 2: Identification of Transistor Amplifier Circuits The Differential Pair The circuit shown is the typical configuration of a differential amplifier The emitter of each transistor is tied together and connected to a constant current source, 𝐼𝑇𝐴𝐼𝐿. These pair of transistors is called the differential pair. The current sharing is controlled by the difference of 𝑉𝑖1 and 𝑉𝑖2. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 33 Lecture No. 2: Identification of Transistor Amplifier Circuits The Differential Pair Amplifies the Difference: The differential pair amplifies the difference between two input voltages. If both inputs are equal, the output remains stable, while any difference between them is amplified. Common-Mode Rejection: It has high common-mode rejection, meaning it can ignore or reject signals that are common to both inputs (such as noise) and only respond to the difference. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 34 Lecture No. 2: Identification of Transistor Amplifier Circuits The Differential Pair Balanced Operation: The two transistors share a common current source, which helps balance the operation of the circuit, reducing distortions and improving performance. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 35 Lecture No. 2: Identification of Transistor Amplifier Circuits The Differential Pair High Common-Mode Rejection Ratio (CMRR): It is effective at rejecting noise and interference that affects both input signals equally, making it highly useful in environments with electrical noise. Linear Gain: The differential pair provides a linear response to small differences in input voltage, making it ideal for amplification in analog circuits like operational amplifiers. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 36 Lecture No. 2: Identification of Transistor Amplifier Circuits The Differential Pair Temperature Stability: Since both transistors are closely matched and share a common current source, the differential pair offers good temperature stability, which reduces drift in output. Low Distortion: Because the transistors operate in a balanced manner, the differential pair has low harmonic distortion, making it suitable for high- fidelity amplification. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 37 Lecture No. 2: Identification of Transistor Amplifier Circuits Differential Amplifier with Resistive Load The circuit shown is the differential amplifier with resistive load (differential output, single supply). Resistors are connected to the collectors of each transistor, and they serve as the load for the amplifier. The outputs are typically taken from the collector of each transistor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 38 Lecture No. 2: Identification of Transistor Amplifier Circuits Differential Amplifier with Active Load (S.E.) In this configuration, transistors are used as the load instead of resistors. These transistors act as active loads, providing higher gain and other benefits compared to resistive loads. Instead of resistors, the collectors of Q1 and Q2 are connected to another pair of transistors (Q3 and Q4) that act as active loads. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 39 Lecture No. 2: Identification of Transistor Amplifier Circuits Summary of Key Differences: Feature Differential Amplifier with Resistive Load Differential Amplifier with Active Load Load Type Resistors Transistors (active loads) Gain Moderate (limited by resistor size) High (due to high output resistance) Power Consumption Higher due to large resistors Lower (no large resistors required) Footprint Larger (resistors take up space) Smaller (transistors save space in ICs) Limited bandwidth due to higher Bandwidth Wide bandwidth impedance Design Complexity Simple More complex UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 40 Lecture No. 2: Identification of Transistor Amplifier Circuits Why is it called “Operational” Amplifier? Why is it called “operational” in the first place?? Is it just an amplifier that “operates” correctly? If that’s the case, all amplifiers should be “operational” amplifiers! However, as we all know, not all amplifiers are operational amplifiers. To answer this question, we should go back in time! Around 1947, in which the word “Operational Amplifier” was first coined! Just imagine, how do people simulate systems without a computer? For example, how can they determine the stability of an airplane? UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 41 Lecture No. 2: Identification of Transistor Amplifier Circuits Why is it called “Operational” Amplifier? Instead of using a digital computer, most engineers back then use analog computers. These computers can compute a specific problem using analog circuits, such as amplifiers! But, how can they simulate the dynamic behavior of a mechanical system? Just remember, we can mathematically model a system using Differential Equations! UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 42 Lecture No. 2: Identification of Transistor Amplifier Circuits Why is it called “Operational” Amplifier? UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 43 Lecture No. 2: Identification of Transistor Amplifier Circuits Why is it called “Operational” Amplifier? Most systems would require a set of complex differential equations! When it comes to designing a control system, it would be difficult to do these calculations by hand! What if we represent these differential equations using a circuit? Therefore, we need a circuit that can perform the following operations: differentiation, integration, and summation. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 44 Lecture No. 2: Identification of Transistor Amplifier Circuits Why is it called “Operational” Amplifier? It is called “Operational” Amplifier because this bad boy can perform some mathematical operations! UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 45 Lecture No. 2: Identification of Transistor Amplifier Circuits The Operational Amplifier An Operational Amplifier behaves quite similar to a differential amplifier. It amplifies the voltage difference between its two inputs! The main difference of an OP-AMP to the differential amplifier is its very high open loop gain! UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 46 Lecture No. 2: Identification of Transistor Amplifier Circuits How to make an OP-AMP? An OP-AMP is typically comprised of three stages Differential Amplifier Stage Additional amplifier stages for more gain Output stage (Voltage Follower) 𝑉+ Differential Second Stage 𝑉𝑂𝑈𝑇 Output Stage Amplifier Amplifier 𝑉− UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 47 Lecture No. 2: Identification of Transistor Amplifier Circuits How to make an OP-AMP? UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 48 Lecture No. 2: Identification of Transistor Amplifier Circuits How to make an OP-AMP? LM2902 OP-AMP LM741 OP-AMP UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 49 Lecture No. 2: Identification of Transistor Amplifier Circuits OP-AMP as a Black Box An operational amplifier can be abstracted as “black box” having two inputs and one output. The op amp symbol distinguishes between the two inputs by the plus and minus sign. Vin1 and Vin2 are called the “noninverting” and “inverting” inputs, respectively. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 50 Lecture No. 2: Identification of Transistor Amplifier Circuits OP-AMP as a Black Box We view the op amp as a circuit that amplifies the difference between the two inputs, arriving at the equivalent circuit depicted in the figure below The voltage gain is denoted by A0: 𝑉𝑜𝑢𝑡 = 𝐴0 (𝑉𝑖𝑛1 − 𝑉𝑖𝑛2 ) *𝐴0 → Open Loop Gain UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 51 Lecture No. 2: Identification of Transistor Amplifier Circuits The Ideal OP-AMP Ideal LM2902 (TI) LM741 (TI) Voltage Gain, ∞ 100,000 200,000 A0 = 𝑉𝑜𝑢𝑡 /(𝑉𝑖𝑛1 − 𝑉𝑖𝑛2 ) Input Impedance, ∞ Several MΩ 2 MΩ 𝑍𝑖𝑛 Output Impedance, < 100 Ω 0 < 100 Ω 𝑍𝑜𝑢𝑡 Speed/Bandwidth, ∞ 1.2MHz 1.5MHz 𝐵 UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 52 Lecture No. 2: Identification of Transistor Amplifier Circuits Operational Amplifier UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 53 Lecture No. 2: Identification of Transistor Amplifier Circuits Operational Amplifier UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering Lecture No. 2: Identification of Transistor Amplifier Circuits Analog Filter Circuits Lecture No. 2: Identification of Transistor Amplifier Circuits UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 55 Module 5: Analog Filter Circuits General Considerations To define the performance parameters of filters, we first take a brief look at some applications. Suppose a cellphone receives a desired signal, 𝑋(𝑓), with a bandwidth of 200 kHz at a center frequency of 900 MHz. Now, let us assume that, in addition to 𝑋(𝑓), the cellphone receives a large interferer centered at 900 MHz + 200 kHz. Since the information is in the signal 𝑋(𝑓), we need to “reject” the interferer by means of a filter. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 56 Module 5: Analog Filter Circuits Filter Characteristics The frequency response of every filter is divided into three bands: Passband; Transition Band; and Stopband Some characteristics of a filter should be considered: ▪ The filter must not affect the desired signal. It must provide a “flat” frequency response across the bandwidth of 𝑋(𝑓). ▪ The filter must attenuate the interferer signal. It must exhibit a “sharp” transition band. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 57 Module 5: Analog Filter Circuits Sample Problem In a wireless application, the interferer in the adjacent channel may be 25 dB higher than the desired signal. Determine the required stopband attenuation of the filter in the figure below if the signal power must exceed the interferer power by 15 dB for proper detection. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 58 Module 5: Analog Filter Circuits Classification of Filters Filters can be categorized according to their various properties. One classification of filters relates to the frequency band that they “pass” or “reject.” The figure shown below is the frequency response of a Low Pass Filter (LPF) Circuit. It allows low frequency signals to pass while rejecting high frequency signals. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 59 Module 5: Analog Filter Circuits Classification of Filters Conversely, a High Pass Filter (HPF) allows high frequency signals to pass and reject low frequency signals. The figure shown below depicts the frequency response of an HPF. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 60 Module 5: Analog Filter Circuits Classification of Filters Some applications call for a Band Pass Filter (BPF). This kind of filter rejects both low and high frequency signals and passes a band in between. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 61 Module 5: Analog Filter Circuits Classification of Filters The figure below summarizes the types of filters. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 62 Module 5: Analog Filter Circuits Classification of Filters Another classification of analog filters concerns their circuit implementation and includes “continuous-time” and “discrete-time” realizations. ▪ Continuous-time → composed of circuit elements such as Resistors, Capacitors, and Inductors. ▪ Discrete-time → Mainly composed of energy storage elements, such as capacitor, and a switch. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 63 Module 5: Analog Filter Circuits Classification of Filters The third classification of filters distinguishes between “passive” and “active” implementations. ▪ Passive Filter incorporates only passive devices such as resistors, capacitors, and inductors. ▪ Active Filter also employs amplifying components such as transistors and op amps. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 64 Module 5: Analog Filter Circuits Classification of Filters: Summary UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 65 Module 5: Analog Filter Circuits First Order Passive Filters A first-order passive filter refers to a filter circuit made up of passive components (resistors, capacitors, or inductors) that has a frequency response defined by a first- order differential equation. These filters are called "first-order" because their roll-off rate is 20 dB per decade (or 6 dB per octave) in the stopband. First-order passive filters can be configured as low-pass or high-pass filters. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 66 Module 5: Analog Filter Circuits First Order Filters: Passive Low Pass Filter A low-pass filter allows signals with frequencies below a certain cutoff frequency to pass through and attenuates (reduces) signals with frequencies above that cutoff. The input signal is applied to the series combination, and the output is taken across the capacitor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 67 Module 5: Analog Filter Circuits First Order Filters: Passive High Pass Filter A high-pass filter allows signals with frequencies above a certain cutoff frequency to pass through and attenuates signals with frequencies below that cutoff. The input signal is applied to the series combination, and the output is taken across the resistor. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 68 Module 5: Analog Filter Circuits First Order Active Filters The simplest way to construct an active filter circuit is to cascade a first stage passive filter into a second stage active circuit such as a non-inverting amplifier. The purpose of the amplifier is to increase the system gain! UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 69 Module 5: Analog Filter Circuits First Order Filters: Active Filters UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 70 Module 5: Analog Filter Circuits First Order Filters: Active Filters Another way to construct an active filter is to use frequency dependent components in the feedback network of an amplifier. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 71 Module 5: Analog Filter Circuits Second Order Filters: Passive Filters Second order filter circuits are typically composed of 2 frequency dependent components. For passive filters, it is typically composed of R, L, and C. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 72 Module 5: Analog Filter Circuits Second Order Filters: Active Filters Typical active second order filters are realized using the Sallen-Key Filter. ▪ Two capacitors are used for the two frequency dependent components. ▪ The circuit shown below is an Active Low Pass Filter. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 73 Module 5: Analog Filter Circuits Second Order Filters: Active Filters The circuit shown below is an Active High Pass Filter. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 74 Module 5: Analog Filter Circuits Band Pass Filters The simplest way to implement a Band Pass Filter is to cascade a Low Pass Filter stage and a High Pass Filter Stage. However, we need to ensure that 𝑓𝑐𝐻𝑃𝐹 < 𝑓𝑐𝐿𝑃𝐹. This kind of BPF is only suitable for wideband applications. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 75 Module 5: Analog Filter Circuits Narrowband BPF Bandpass filters for narrowband applications has a transfer function of 𝐾𝑠 𝐻 𝑠 = 𝜔𝑛 2 𝑠 + 𝑠 + 𝜔𝑛2 𝑄 𝜔𝑛 → Natural Frequency In this case, it is the same as the center frequency, 𝜔0. 𝑄 → 𝑄𝑢𝑎𝑙𝑖𝑡𝑦 𝑓𝑎𝑐𝑡𝑜𝑟 It is the ratio of the center frequency, 𝜔0, to the bandwidth, 𝐵𝑊. Higher Q factor → The filter is more selective. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 76 Module 5: Analog Filter Circuits Passive Narrowband BPF Narrowband BPF can be implemented using passive elements such as resistors, inductors, and capacitors as shown in the figure. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 77 Module 5: Analog Filter Circuits Active Narrowband BPF An active narrowband BPF is implemented using a Multiple Feedback Filter which is shown in the figure. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering Lecture No. 2: Identification of Transistor Amplifier Circuits Output Stages and Power Amplifiers Lecture No. 2: Identification of Transistor Amplifier Circuits UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 79 Module 6: Output Stages and Power Amplifiers Emitter Follower as a Power Amplifier An Emitter Follower is a common type of transistor amplifier configuration, also known as a common-collector amplifier. It is widely used as a power amplifier due to its high current gain, low output impedance, and ability to drive heavy loads such as speakers or motors. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 80 Module 6: Output Stages and Power Amplifiers Push-Pull Stage UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 81 Module 6: Output Stages and Power Amplifiers Push-Pull Stage A push-pull power amplifier is a type of amplifier design where two active devices (typically transistors) alternately handle the positive and negative halves of the input signal. This configuration is commonly used in audio and RF applications due to its efficiency and ability to deliver significant output power. The push-pull amplifier achieves higher efficiency (around 70- 78% in theory for a Class B amplifier) because each transistor is only active for half the cycle, reducing power dissipation. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 82 Module 6: Output Stages and Power Amplifiers Push-Pull Stage In basic Class B push-pull amplifiers, there's a small delay or gap when switching from the positive to negative transistors. This leads to crossover distortion, a form of distortion that occurs when neither transistor is conducting during the transition between signal halves. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 83 Module 6: Output Stages and Power Amplifiers Improved Push-Pull Stage The distortion arises from the input connection Since both base terminals are tied together, the two transistors cannot turn ON simultaneously around 𝑉𝑖𝑛 = 0𝑉 This can be solved by introducing a DC voltage source in between the two base terminals as shown. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 84 Module 6: Output Stages and Power Amplifiers Improved Push-Pull Stage In an improved push-pull stage amplifier, the circuit operates in Class AB, which combines the advantages of Class A and Class B amplification. The goal is to reduce crossover distortion while maintaining high efficiency. The improved push-pull amplifier typically uses complementary transistors (one NPN and one PNP), which allows for symmetrical amplification of both positive and negative signal halves. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 85 Module 6: Output Stages and Power Amplifiers Power Amplifier Classes The emitter follower and push-pull stages studied in this chapter exhibit distinctly different properties: In the former, the transistor conducts current throughout the entire cycle, and the efficiency is low. In the latter, each transistor is on for about half of the cycle, and the efficiency is high. These observations lead to different “PA classes.” UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 86 Module 6: Output Stages and Power Amplifiers Power Amplifier Classes Class A Each transistor is conducting for the whole cycle Conduction angle = 360° Example: Emitter Follower as a Power Amplifier Class B Each transistor is conducting only for half of the cycle Conduction angle = 180° Example: Push-Pull Stage Take note: due to the dead zone, actual conduction angle < 180° Class AB Each transistor is conducting slightly greater than the half of the cycle Conduction angle → Slightly greater than 180° Example: Improved Push-Pull Stage UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 87 Module 6: Output Stages and Power Amplifiers Power Amplifier Classes Collector current waveforms for (a) Class A, (b) Class B, and (c) Class AB operation UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 88 Module 6: Output Stages and Power Amplifiers Power Amplifier Classes Efficiency versus Linearity Trade-off We can observe in the previous slide, Less conduction angle, Higher Efficiency Because the power drawn from the load is divided into 𝑃𝑜𝑢𝑡 and 𝑃𝑐𝑘𝑡 𝑃𝑐𝑘𝑡 can be reduced by reducing the conduction angle, resulting to a higher efficiency! However, a transistor with a conduction angle less than 𝟑𝟔𝟎° is prone to produce distortions in the output hence reducing the linearity of the amplifier! A proper design of output filter is required to produce a high-fidelity output! UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 89 Module 6: Output Stages and Power Amplifiers Power Amplifier Classes Amplifier Class Conduction Angle Max Efficiency A 360° 25% B 180° 78.5398% AB Slightly > 180° Slightly < 78.5398% C < 180° > 78.5398% D ≪ 180° Up to 90% UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 90 Lecture No. 2: Identification of Transistor Amplifier Circuits Lecture No. 2 References: R. Boylestad and L. Nashelsky, Electronic Devices and Circuit Theory. Harlow: Pearson Education, 2014. UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering  REF-SPP-COE-ECE-DEP-GCV-I01-R00-09262020 | 91 Lecture No. 2: Identification of Transistor Amplifier Circuits End of Discussion UNIVERSITY Department OF SANTO TOMAS of Electronics – DEPARTMENT OF ELECTRONICS ENGINEERING Engineering