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  • Anna university - ACEW
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LIST OF EXPERIMENTS ELECTRONICS CIRCUITS LABORATORY LTPC 1. Characteristics of semiconductor diode and zener diode . 2. Characteristics of transistor under CE, CB and CC . 3. Characteristics of FET . 4. Characteristics of UJT . 5. Characteristics of SCR, DIAC and TRIAC. 6. Photodiode, Phototransistor characteristics and study of light activated relay circuit. 7. Static characteristics of Thermistors. 8. Single phase half wave and full wave rectifiers with inductive and capacitive filters. 9. Differential amplifiers using FET. 10. Study of CRO. 11. Series and parallel resonance circuits. 12. Realization of passive filters.

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Ex.No.1a CHARACTERISTICS OF PN JUNCTION DIODE AIM: To study the PN junction diode characteristics under Forward & Reverse bias conditions. APPARATUS REQUIRED: S.No. 1 2 3 Name Range COMPONENTS REQUIRED: Type Qty R.P.S Ammeter Voltmeter S.No. Name 1 Diode 2 Resistor 3 4 Range Type Bread Board Wires THEORY: A PN junction diode is a two terminal junction device. It conducts only in one direction (only on forward biasing). FORWARD BIAS: On forward biasing, initially no current flows due to barrier potential. As the applied potential exceeds the barrier potential the charge carriers gain sufficient energy to cross the potential barrier and hence enter the other region. The holes, which are majority carriers in the P-region, become minority carriers on entering the N-regions, and electrons, which are the majority carriers in the N-region, become minority carriers on entering the P-region. This injection of Minority carriers results in the current flow, opposite to the direction of electron movement. Qty

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REVERSE BIAS: On reverse biasing, the majority charge carriers are attracted towards the terminals due to the applied potential resulting in the widening of the depletion region. Since the charge carriers are pushed towards the terminals no current flows in the device due to majority charge carriers. There will be some current in the device due to the thermally generated minority carriers. The generation of such carriers is independent of the applied potential and hence the current is constant for all increasing reverse potential. This current is referred to as Reverse Saturation Current (IO) and it increases with temperature. When the applied reverse voltage is increased beyond the certain limit, it results in breakdown. During breakdown, the diode current increases tremendously. PROCEDURE: FORWARD BIAS: 1. Connect the circuit as per the diagram. 2. Vary the applied voltage V in steps of 0.1V. 3. Note down the corresponding Ammeter readings I. 4. Plot a graph between V & I OBSERVATIONS 1. Find the d.c (static) resistance = V/I. 2. Find the a.c (dynamic) resistance r = V / I (r = V/I) = V2  V1 . I 2  I1 3. Find the forward voltage drop = [Hint: it is equal to 0.7 for Si and 0.3 for Ge] REVERSE BIAS: 1. Connect the circuit as per the diagram. 2. Vary the applied voltage V in steps of 1.0V. 3. Note down the corresponding Ammeter readings I. 4. Plot a graph between V & I 5. Find the dynamic resistance r = V / I.

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FORMULA FOR REVERSE SATURATION CURRENT (IO): Io = I/[exp(V/VT)]-1 Where VT is the voltage equivalent of Temperature = kT/q -k is Boltzmann’s constant, q is the charge of the electron and T is the temperature in degrees Kelvin.  =1 for Silicon and 2 for Germanium CIRCUIT DIAGRAM: FORWARD BIAS: 470  (0-10)V RPS + + (0-100)mA, MC + a + a a a a A A A + (0-15)V, MC + REVERSE BIAS: (0-500)µA,MC 470  (0-30)V RPS + + + a + a a a a A A A Specification for 1N4001: Silicon Diode Peak Inverse Voltage: 50V + + (0-30)V, MC

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