Question

Al List two non-ideal characteristics of BJT and briefly explain their relationship in the shape of the curve of common-emitter current gain (BF) versus Ic (10 points) B) Explain the punchthrough voltage of a BJT and list & possible way to increase the punchthrough voltage of a BJT. (5 points)

Answer 1

(A) Non-ideal characteristics of BJT- Early effect rightarrow The process where the effective Base width of the transistor is altered by v_cj (Junction voltage) is called the Base width modulation or early effect WB' = effective Base width of transistor reduced. the property of Base narrowing in the transistor is related with early effect. consequence in a Transistor because of early effect WB' Reduced therefore transit time reduced so Transistor become faster the collector current increase slightly Base current Reduce beta of transistor increase by a large value Couse alpha increase slightly it WB' increase slightly so Base current is large so i. e Reduce. High level Injection From emitter rightarrow when the Base emitter bias becomes very high, low level condition break Down. when the injected minority carrier concentration is very High, the full dependence on the Applied voltage begins to deviate from the simple exponential dependence. The main cause of deviation from the feet that the integrated majority