Question

The phenomenon known as Early "Effect" in a bipolar transistor refers to a reduction of the effective base – width caused by 

(a) Electron – hole recombination at the base 

(b) The reverse biasing of the base – collector junction 

(c) The forward biasing of emitter – base junction 

(d) The early removal of stored base charge during saturation – to – cutoff switching

Answer 1

Explanation:

 For the transistor in common – emitter configuration the collector current for a given IB is expected to be independent of V_CE. This is true when base width is constant, but when the base collector voltage (reverse bias) is increased the base width will be reduced. 

This reduced base width causes the minority carries to increase, which causes increase in diffusion current. As a result β will be increased i.e. I_C increases with V_CE. This deviation is known as Early effect or base width modulation. 

An extrapolation of collector currents gives interaction with V_CE axis, which is called Early voltage (V_A)