Electronic Tests and Measurements ECE 331 Past Paper PDF 2024

‫اﻟﻔﺻل اﻟدراﺳﻰ اﻟﺳﺎﺑﻊ‬ ‫اﻟﻣﺳﺗوى اﻟراﺑﻊ‬ 2024 ‫ﺧرﯾف‬ Electronic Tests and Measurements (1) ECE 331 Cr-3 L- 2 Tut- 0 P- 3 Fall semester S-7 (2024-2025) Learning is teaching...

‫اﻟﻔﺻل اﻟدراﺳﻰ اﻟﺳﺎﺑﻊ‬ ‫اﻟﻣﺳﺗوى اﻟراﺑﻊ‬ 2024 ‫ﺧرﯾف‬ Electronic Tests and Measurements (1) ECE 331 Cr-3 L- 2 Tut- 0 P- 3 Fall semester S-7 (2024-2025) Learning is teaching Engineering is and education a quality and cost ‫اﻷﺳﺑوع اﻟﺳﺎﺑﻊ‬ Resistance Levels One of the important parameters for the diode is the resistance at the point or region of operation. The ideal diode, therefore, is a short circuit for the region of conduction (a). The ideal diode, therefore, is an open circuit in the region of non-conduction (b). 21 November 3 Resistance Levels DC or Static Resistance (at any point in the curve) VD RD = ID AC or Dynamic Resistance ∆Vd rd = ∆I D Average AC ∆Vd rd = ∆I D From point to point 21 November 4 Resistance Levels cont… 5 21 November 7 V-I characteristics of PN junction diode Diode Testing (forward bias) Ohmmeter Testing  The characteristic curve for a real p–n junction =I D I S eVD / nVT − I S Note that above the axis the scale is in milliamperes (mA), whereas below the axis it is in picoamperes (pA). 21 November  In toto Current flows through diode in forward bias and does not flow through diode in reverse bias i.e. diode can pass current only in one direction. Zener diode Zener Diode Once the breakdown voltage is reached, a large number of minority carriers suddenly appears in the depletion V=I Rz layer and the diode starts to conduct heavily. This results from two mechanisms known as avalanche and zener breakdown. VQ RZ = (Static rsistance) IQ - Vz + + Vz - ∆V rZ = (Dynamic resistance) ∆I Iz If Zener V-I Curve “Zooming in” Zener v-i characteristic Volt-ampere characteristic for a silicon diode at a temperature of 300 K. Notice the changes of scale. Zener diode characteristics with the equivalent model of each region Current-voltage characteristic of a Zener diode with a breakdown voltage of 17 volts. Notice the change of voltage scale between the forward biased (positive) direction and the reverse biased (negative) direction. Zener diode A Zener diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage", "Zener voltage", "avalanche point", or "peak inverse voltage". Applications include providing a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses. Waveform clipper Two Zener diodes facing each other in series will act to clip both halves of an input signal. Waveform clipper can be used to not only reshape a signal, but also to prevent voltage spikes from affecting circuits that are connected to the power supply. Voltage shifter A Zener diode can be applied to a circuit with a resistor to act as a voltage shifter. This circuit lowers the input voltage by a quantity that is equal to the Zener diode's breakdown voltage. ‫اﻷﺳﺑوع اﻟﺛﺎﻣن‬  The Biased PN Junction Forward Bias: In forward bias the depletion region shrinks slightly in width. With this shrinking the energy required for charge carriers to cross the depletion region decreases Vapplied > 0 exponentially. The barrier potential of the diode is the voltage at which appreciable current starts to flow through the diode. Reverse Bias: Under reverse bias the depletion region widens. A small leakage current, Is (saturation current) flows Vapplied < 0 under reverse bias conditions. This saturation current is made up of electron-hole pairs being produced in the depletion region.  Types of Diodes and Their Uses PN Junction Are used to allow current to flow in one direction Diodes: while blocking current flow in the opposite direction. A K P n Schematic Symbol for a PN Representative Structure for Junction Diode a PN Junction Diode Zener Diodes: Are specifically designed to operate under reverse breakdown conditions. These diodes have a very accurate and specific reverse breakdown voltage. A K Schematic Symbol for a Zener Diode  Types of Diodes and Their Uses Schottky These diodes are designed to have a very fast Diodes: switching time which makes them a great diode for digital circuit applications. They are very common in computers because of their ability to be switched A K on and off so quickly. Schematic Symbol for a Schottky Diode Shockley The Shockley diode is a four-layer diode while other Diodes: diodes are normally made with only two layers. These types of diodes are generally used to control the average power delivered to a load. A K Schematic Symbol for a four-layer Shockley Diode  Types of Diodes and Their Uses Light-Emitting Light-emitting diodes are designed with a very large Diodes: bandgap so movement of carriers across their depletion region emits photons of light energy. Lower bandgap LEDs (Light-Emitting Diodes) emit infrared radiation, while LEDs with higher bandgap energy emit visible light. Many spot lights are now starting to use LEDs because they are extremely bright and last longer than regular bulbs for a relatively low cost. The arrows in the LED A K representation indicate emitted light. Schematic Symbol for a Light-Emitting Diode  Types of Diodes and Their Uses Photodiodes: While LEDs emit light, Photodiodes are sensitive to received light (LADs). They are constructed so their pn junction can be exposed to the outside through a clear window or lens. A K In Photoconductive mode the saturation current increases in proportion to the intensity of the The arrows in the LED received light. This type of diode is used in CD representation indicate players. absorbed light. In Photovoltaic mode, when the pn junction is exposed to a certain wavelength of light, the diode generates voltage and can be used as an energy λ source. This type of diode is used in the A K production of solar power. Schematic Symbols for Photodiodes ‫اﻷﺳﺑوع اﻟﺗﺎﺳﻊ‬