## Wednesday, October 5, 2011

### h-PARAMETERS OF CE CONFIGURATION Electronic devices and circuits lab manual

h-PARAMETERS OF CE CONFIGURATION
AIM:   To calculate the H-parameters of transistor in CE configuration.
APPRATUS:         Transistor BC 107
Resistors 100 K Ώ 100 Ώ
Ammeter (0-200µA), (0-200mA)
Voltmeter (0-20V) - 2Nos
Regulated Power Supply (0-30V, 1A) - 2Nos
THEORY:
INPUT CHARACTERISTICS:
The two sets of characteristics are necessary to describe the behavior of the CE configuration one for input or base emitter circuit and other for the output or collector emitter circuit.
In input characteristics the emitter base junction forward biased by a  very small voltage VBB  where as collector base junction reverse biased by a very large voltage VCC. The input characteristics are a plot of input current IB Vs the input voltage VBE ­ for a range of values of output voltage VCE . The following important points can be observed from these characteristics curves.
1.    The characteristics resemble that of CE configuration.
2.    Input resistance is high as IB increases less rapidly with VBE
3.    The input resistance of the transistor is the ratio of change in base emitter voltage ΔVBE to change in base current ΔIB at constant collector emitter voltage ( VCE) i.e... Input resistance or input impedance hie = ΔVBE / ΔIB at VCE constant.

OUTPUT CHARACTERISTICS:
A set of output characteristics or collector characteristics are a plot of out put current IC VS output voltage VCE for a range of values of input current IB .The following important points can be observed from these characteristics curves:-
1. The transistor always operates in the active region. I.e. the collector current
IC increases with VCE very slowly. For low values of the VCE the IC increases rapidly with a small increase in VCE .The transistor is said to be working in saturation region.
Output resistance is the ratio of change of collector emitter voltage ΔVCE , to change in collector current ΔIC with constant IB. Output resistance or Output impedance hoe = ΔVCE / ΔIC at IB constant.
Input Impedance hie = ΔVBE / ΔIB at VCE constant
Output impedance hoe = ΔVCE / ΔIC at IB constant
Reverse Transfer Voltage Gain hre = ΔVBE  / ΔVCE at IB constant
Forward Transfer Current Gain hfe =  ΔIC / ΔIB at constant VCE

CIRCUIT DIAGRAM:

PROCEDURE:
1. Connect a transistor in CE configuration circuit for plotting its input and output characteristics.
2. Take a set of readings for the variations in IB with VBE at different fixed values of output voltage VCE .
3. Plot the input characteristics of CE configuration from the above readings.
4. From the graph calculate the input resistance hie and reverse transfer ratio hre by taking the slopes of the curves.
5. Take the family of readings for the variations of IC with VCE  at different values of fixed IB.
6. Plot the output characteristics from the above readings.
7. From the graphs calculate hfe ands hoe by taking the slope of the curves.
Tabular Forms
Input Characteristics
 S.NO VCE=0V VCE=6V VBE(V) IB(μA) VBE(V) IB(μA)

Output Characteristics
 S.NO IB = 20 µA IB = 40 µA IB = 60 µA VCE (V) IC(mA) VCE (V) IC(mA) VCE (V) IC(mA)

MODEL WAVEFORM:  Input Characteristics

Output Characteristics

RESULT: The H-Parameters for a transistor in CE configuration are calculated from the input and output characteristics.