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EXPERIMENT NO-3

AIM OF THE EXPERIMENT

VI characteristics of a PN junction diode

for forward and reverse biasing . Determination of D.C and

A.C resistance.

OBJECTIVE Plot the graph V vs. I for forward bias and reverse bias.

Find the DC and AC resistance for forward bias.

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APPARATUS REQUIRED

SL . NO COMPONENT/EQUIPMENT SPECIFICATION QUANTITY

1 Micro lab kit 1

2 DC power supply 0-30 volt 2

3 Multi meter 2

4 Diode IN4007 1

5 Zener diode 6.7 V 1

6 Resistor 1 K 1

7 Connecting wires As required

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THEORY

SEMICONDUCTOR DIODE:

Diode is a two terminal electronic component with

asymmetric conductance, it has low resistance to current

flow in one direction .

There are two types of semiconductor diode:-i) P TYPE

ii) N -TYPE

TYPES OF BIASING

A. No biasing

B. Forward biasing

C. Reverse biasing

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DIODES

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FORWARD BIASING(VD

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FORWARD BIASING OF P-N JUNCTION

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REVERSE BIASING(Vd

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REVERSE BIASING OF P-N JUNCTION

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Shockleys equation

Where,

Is = reverse saturation currentVD= forward bias voltage applied across the dioden = ideality factor

VT =KT/qK = Boltzmann's constant

T= absolute temperature

q = magnitude of electronic charge

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CIRCUIT DIAGRAM OF FORWARD BIAS OF

DIODE

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CIRCUIT DIAGRAM OF REVERSE BIAS OF ZENER DIODE:

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PROCEDURE

FORWARD BIASINGI. Connect the circuit as per the circuit diagram.

II. Vary the power supply voltage(Vi) 0-5 in such a way that the

readings are taken in step of 0.2 V.

III. Note down the forward voltage (V f) to the corresponding

forward current(If).

IV. Plot the graph V vs. I.

V. Find the dynamic resistance and static resistance from the

graph.

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REVERSE BIASING:

I. Connect the circuit as per the circuit diagram.

II. Vary the power supply voltage(Vi) 0-15 in steps of 1 volt.

III. Note down the reverse voltage (Vr) to the corresponding

reverse current (Ir).

IV. Plot the graph V vs. I.

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CHARACTERISTIC CURVE FOR FORWARD BIASOF DIODE

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OBSERVATION

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OBSERVATION

FORWARD BIASING

REVERSE BIASING

SL NO I/P VOLTAGE (Vi) Forward voltage ( Vr) Forward current (If)

SL NO I/P VOLTAGE(V i) Reverse voltage ( Vr) Reverse current( Ir)

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EXPERIMENT NO- 4

AIM OF THE EXPERIMENT

Diode as half wave and full wave rectifier. Calculation of

D.C current and ripple factor for resistive load and capacitive

load.

OBJECTIVES:

I. Find out the average value, RMS value and Ripple factor.

II. Trace the I/O wave forms for half wave and full wave

rectifier.

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APPARATUS REQUIRED

S L NO COMPONENT/EQUIPMENT SPECIFICATION QUANTITY

1 Micro lab kit 1

2 CRO 20 MHZ 1

3 CRO probes 2

4 Diode IN4007 4

5 Resistor 1K 1

6 Capacitors 470F 1

7 Connecting wires As per

requirement

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THEORY

RECTIFIER:

When a diode is employed in the rectification process it is

termed as a rectifier.

The power gain is more as compared to the diodes used in the

other purposes.

Generally the sinusoidal and square wave signals are applied

to it.

There are two types of rectifires

i) HALF WAVE RECTIFIERii) FULL WAVE RECTIFIER

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HALF WAVE RECTIFIER

I. During the interval 0-T/2 the polarity of the applied voltageVi is much more than the polarity of the diode andpressures the diode to turn ON.

II. So the o/p waveform in this time interval is an exact replicaof i/p waveform.

III. During the interval T/2-T the polarity of the i/p Vi is reversedand the polarity across the diode produces an OFF statewith an open circuit equivalent.

Vd.c = 0.318 Vm

The process of removing one half of the i/p signal toestablish a dc level is called half wave rectifier.

PIV rating >=Vm

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FULL WAVE BRIDGE TYPE RECTIFIER

I. Full wave rectification is a process by which 100% of d.clevel can be obtained from a sinusoidal input.

II. During the period 0-T/2 the diode D2 and D3 are conducting

where are D1 and D4 are in OFF state.

III. Since the diodes are ideal ,the load voltage Vo =ViIV. For theve region of the i/p the conducting diodes are D1

and D4 ,where as D2 and D3 are in OFF state.

Here also Vo =Vi

Vd.c =2(0.318 Vm) =0.636 VmPIV >== Vm

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FULLWAVE CENTER TAPPED RECTIFIER

I. Here an i/p signal is applied across each section of the

secondary of the transformer of center type.

II. During the +ve half cycle, the D1 is short circuited and D2 is

open circuited and a o/p voltage is applied.

III. Similarly during theve half cycle D1 is open circuited and

D2 is short circuited but maintain the same polarity for the

voltage across the resistor R.

PIV>=2Vm

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CIRCUIT DIAGRAM

CIRCUIT DIAGRAM OF HALF WAVE RECTIFIER

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CIRCUIT DIAGRAM OF FULL WAVE BRIDGE

RECTIFIER

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CIRCUIT DIAGRAM OF FULL WAVE CENTER

TAP RECTIFIER

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PROCEDURE

I. Connect the circuit as per the circuit diagram.

II. Observe the I/O signal of the CRO.

III. Measure the input voltage and the average and r.m.s value

of output voltage for half wave and full wave rectifier.

IV. Calculate the ripple factor.

V. Trace the output wave forms with and without capacitor

filter.

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WAVE FORMS

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INPUT AND OUTPUT OF FULL WAVE CT

RECTIFIER

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INPUT AND OUTPUT OF FULLWAVE BRIDGE

RECTIFIER

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OBSERVATION

PARAMETERS H /W RECTIFIER F/W RECTIFIER(CT) F/W RECTIFIER

(BRIDGE)

Vm

Vavg

Vrms

RIPPLE FACTOR

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CALCULATION

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PRECAUTION:

Short circuit should be avoided.

Handle the materials carefully.

CONCLUSION