Relationship between current amplification factors - alpha and beta for transistor:-
Transistor Act as a Switch(on/off):-
Characteristics of Common emitter (CE) Configuration
The characteristic of the common emitter transistor circuit is shown in the figure below. The base to emitter voltage varies by adjusting the potentiometer R1. And the collector to emitter voltage varied by adjusting the potentiometer R2. For the various setting, the current and voltage are taken from the milliammeters and voltmeter. On the basis of these readings, the input and output curve plotted on the curve.
Input Characteristic Curve
The curve plotted between base current IB and the base-emitter voltage VEB is called Input characteristics curve. For drawing the input characteristic the reading of base currents is taken through the ammeter on emitter voltage VBE at constant collector-emitter current. The curve for different value of collector-base current is shown in the figure below.
The curve for common base configuration is similar to a forward diode characteristic. The base current IB increases with the increases in the emitter-base voltage VBE. Thus the input resistance of the CE configuration is comparatively higher that of CB configuration.
The effect of CE does not cause large deviation on the curves, and hence the effect of a change in VCE on the input characteristic is ignored.
Input Resistance: The ratio of change in base-emitter voltage VBE to the change in base current ∆IB at constant collector-emitter voltage VCE is known as input resistance, i.e.,
Output Characteristic
In CE configuration the curve draws between collector current IC and collector-emitter voltage VCE at a constant base current IB is called output characteristic. The characteristic curve for the typical NPN transistor in CE configuration is shown in the figure below.
In the active region, the collector current increases slightly as collector-emitter VCE current increases. The slope of the curve is quite more than the output characteristic of CB configuration. The output resistance of the common base connection is more than that of CE connection.
The value of the collector current IC increases with the increase in VCE at constant voltage IB, the value β of also increases.
When the VCE falls, the IC also decreases rapidly. The collector-base junction of the transistor always in forward bias and work saturate. In the saturation region, the collector current becomes independent and free from the input current IB
In the active region IC = βIB, a small current IC is not zero, and it is equal to reverse leakage current ICEO.
Output Resistance: The ratio of the variation in collector-emitter voltage to the collector-emitter current is known at collector currents at a constant base current IB is called output resistance ro.
The value of output resistance of CE configuration is more than that of CB
SEMICONDUCTOR TYPE | Intrinsic Extrinsic p-Type n-Type:-
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