Mixed Signals PDF

**[Mixed Signals ]** \- is a system that contains both digital and analog signals; such system can be an integrated chip, a PCB product, or a system of components. -They all combine together in a hierarchy to come up with a larger device of powerful multi-functionality, like smart phones. -syste...

**[Mixed Signals ]** \- is a system that contains both digital and analog signals; such system can be an integrated chip, a PCB product, or a system of components. -They all combine together in a hierarchy to come up with a larger device of powerful multi-functionality, like smart phones. -systems can be found everywhere, especially in consumer electronics that can interact with the outer environment using a variety of sensors. Three examples on mixed-signal systems: **1. Microcontrollers and SoCs** [ **Microcontrollers**] has been the **backbone** of the mixed-signal technologies , well-selected MCU can save a lot of costs and space, reducing the need for external ICs, like operational amplifiers. **System-on-Chips (SoC),** particularly Analog-Mixed-Signal SoCs (AMS-SoC) \- more powerful and usually dedicated to a common function of consumer electronics; such as audio/video processing, as found in most Bluetooth headsets and IP cameras. **[Sensor]** \- is a device, module, machine, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. **[Active Sensors]** are those which require an external excitation signal or a power signal. **[Passive Sensors]**, on the other hand, do not require any external power signal and directly generates output response. based on conversion phenomenon i.e., the input and the output. Some of the common conversion phenomena Are : **Photoelectric, Thermoelectric, Electrochemical, Electromagnetic,** **Thermooptic, etc.** The other names of voltage follower are: **[- Isolation Amplifier ]** **[- Buffer Amplifier ]** **[- Unity-Gain Amplifier]** Applications of Voltage Follower: **[1. Buffers for logic circuits. ]** **[2. In Sample and hold circuits. ]** **[3. In Active filters. ]** **[4. In Bridge circuits via transduce]** Voltage follower is implemented in circuits for reasons. **[1. isolating purpose ]** **[2. buffering the output voltage from an electrical or electronic circuit to get the desired voltage to the connected load.]** **[Unit of resistance - ohms (]**abbreviated Ω) **[Linear Applications of Op-Amp ]** \- the output voltage or current which is directly proportional to either input voltage or current. **[Non-linear Applications of Op-Amp ]** \- is one in which the output signal is not directly proportional to the input signal. **[Voltage Follower ]** \- is an Op-amp circuit whose output voltage straight away follows the input voltage. \- that is output voltage is equivalent to the input voltage. \- Op-amp circuit does not provide any amplification. \- Thus, **[voltage gain is equal to 1. ]** \- They are similar to discrete emitter follower. Examples of Linear application of Op-Amp **[Inverting amplifiers ]** \- (also known as an inverting operational amplifier or an inverting op-amp) -produces an output which is out of phase with respect to its input by 180 degrees. **[Non - Inverting amplifiers ]** **[- or non inverting op amp]** uses op amp as main element. \- is an op amp based amplifier with positive voltage gain. **Advantages of Voltage Follower** [1. Provides p**ower gain** and **current gain**. ] [2. **Low output i**mpedance to the circuit which uses the output of the voltage follower. ] [3. The Op-amp **takes zero current** from the input. ] [4. Loading effects can be avoided.] **[Anti-Logarithmic Amplifier (anti-log amplifier)]** \- is an electronic circuit that produces an output that is proportional to the antilogarithm of the applied input. I**[ntegrator Op-amp ]** \- produces an output voltage that is both proportional to the amplitude and duration of the input signal. ***[differentiator]*** circuit produces a **constant** output voltage for a steadily changing input voltage. ***[integrator]*** circuit produces a s**teadily** changing output voltage for a constant input voltage. **[Voltage Comparator]** \- is a circuit which **compares two voltages and** **switches the output to either high or low state** depending upon which voltage is higher. **[Zero Crossing Detectors ]** \- An op-amp detector that has the ability to detect the change from positive to negative or negative to a positive level of a sinusoidal waveform. \- it detects the **[zero crossing]** of the applied ac signal. **Non Zero Crossing Detectors** **-**modified level of zero level detector to detect positive signal. How is the reference voltage be applied? Three ways: **battery, voltage, zenor diode** **[Precision Rectifier ]** \- also known as a **super diode**, is a configuration obtained with one or more operational amplifiers in order to have a circuit behave like an ideal diode and rectifier. **[Clock Period]** -- this is the time between successive transitions in the same direction, ie, between two rising or two falling edges. **[Duty Cycle]** -- this is the **ratio of the clock** width to the clock period. **[Clock Width]** -- this is the time during which the value of the clock signal is equal to a logic "1", or HIGH. **Formula of voltage gain:** **[OHMS LAW]**  **[Logarithmic amplifier (log amplifier) ]** \- is an electronic circuit that produces an output that is proportional to the logarithm of the applied input. **[instrumentation Amplifier ]** \- is used to amplify very low-level signals, rejecting noise and interference signals. Examples: ** Heartbeats** ** blood pressure** ** Temperature** ** earthquakes and so on.** **[The advantages of the instrumentation amplifier: ]** The gain of a three op-amp instrumentation amplifier circuit can be **easily varied** by adjusting the value of only one resistor Rgain. The gain of the amplifier **depends only on the external resistors used.** The *[input impedance]* is **very high due to the emitter follower configurations** of amplifiers 1 and 2 The *[output impedance]* of the instrumentation **amplifier is very low due** to the difference amplifier3. The **CMRR of the op-amp 3 is very high** and almost all of the common mode signal will be rejected. **[Voltage to Current Converter]** (**V to I converter)** \- is an electronic circuit that takes current as the input and produces voltage as the output. [ ***differentiator*** ] *[-]*circuit produces a constant output voltage for a steadily changing input voltage. **[Schmitt Trigger ]** \- avoids the problem in comparator. \- is **form of comparator circuit** that has hysteresis or different input switching levels to change the output between the two states -invented by an American scientist named **Otto Schmitt** [(**I to V converter)** ] \- is an electronic circuit that takes current as the input and produces voltage as the output. **three types of clock pulse generation circuits:** **[Astable]** -- A ***free-running multivibrator*** that has NO stable states but switches continuously between two states this action produces a train of square wave pulses at a fixed frequency. **[Monostable]** -- A ***one-shot multivibrator*** that has only ONE stable state and is triggered externally with it returning back to its first stable state. **[Bistable]** -- A ***flip-flop* that has TWO stable states** that produces a single pulse either positive or negative in value **[DAC -]** converts the processed digital signal back into the analog signal that is used by audio output equipment such as a speaker. **[ADC]**- converts the analog signal collected by audio input equipment, such as a microphone, into a digital signal that can be processed by computer. **[resistors]** are scaled to represent weights for the different input bits. The most inexpensive type of ADC is a **[Successive-Approximation ADC.]** **[Sampling Frequency]** [**-**] means the converter is sampling the analog audio signal and doing analog to digital conversion at 44000 times per second. The performance of ADCs and DACs mainly depends on their **[Resolution and Speed.]** Resolution of a converter is expressed in the number of **[Bit.]** For an ADC, the Resolution states the number of intervals or levels which can be divided from a certain analog input range. An n-bit ADC has the resolution of **[1 / 2n]** The **[higher the Sampling Frequency,]** the **[lower the distortion]** and the **[better the sound quality. ]** ANALOG TO DIGITAL CONVERTER It is the number of times that the converter samples the analog signal, its unit is **[Hertz (Hz)]** **[Differential Amplifier ]** \- is a device which is used to amplify the difference between the voltages applied at its inputs. **two types:** 1\. Differential amplifiers built using transistors, either Bipolar Junction Transistors (BJTs) or Field Effect Transistors (FETs) 2. Differential amplifiers built using Op-Amps. ***Operational amplifiers*** \- are **linear devices** that have all the properties required for nearly ideal DC amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation. -is fundamentally a **voltage amplifying device** designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. \- is basically a **three-terminal device** which consists of two high impedance inputs four different classifications of operational amplifier gain: ** Voltage** -- Voltage "in" and Voltage "out" **Current** -- Current "in" and Current "out" ** Transconductance** -- Voltage "in" and Current "out" **Transresistance** -- Current "in" and Voltage "out" **[output voltage signa]**l -from an Operational Amplifier is the difference between the signals being applied to its two individual inputs. **[Infinite]** -- Input impedance is the ratio of input voltage to input current and is assumed to be infinite to prevent any current flowing from the source supply into the amplifiers input circuitry ( I IN = 0 ). **[Open-loop]** gain is the gain of the op-amp without positive or negative feedback and for such an amplifier the gain will be infinite but typical real values range from about 20,000 to 200,000. **[Zero]** -- The output impedance of the ideal operational amplifier is assumed to be zero acting as a perfect internal voltage source with no internal resistance so that it can supply as much current as necessary to the load. **What an Operational Amplifier Can Do?** [ Enables substantial amplification of an input signal ] \- When an operational amplifier is combined with an amplification circuit, it can amplify weak signals to strong signals.It behaves like a megaphone where the input signal is a person's voice and the megaphone is the operational amplifier circuit. [ Enables elimination of noise from an input signal ] \- By operating as a filter of input signals, the operational amplifier circuit is able to extract the signal with the target frequency. **[Things to conisder in selecting operational amplifier]** 1.Check the operating voltage 2.Check the input signal frequency. 3.Check the current consumption. 4.Check the signal amplification accuracy. **3 OP- AMP applications:** **[1. Amplification ]** \- The amplified output signal from the Op Amp is the difference between the two input signals. 2. Voltage follower **[3. Comparator ]** -Operational amplifier compares the voltage applied at one input to the voltage applied at the other input. \- comparator produces l**imited output voltages which can easily** interface with digital logic, even though compatibility needs to be Verified.