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GATE 2014 EE (EE2) – Question 32

Analog and Digital Electronics · Amplifiers: biasing, equivalent circuit and frequency response · 1 mark · Numerical answer

The transistor shown should always be active. Given V_CE(sat) = 0.2 V and V_BE = 0.7 V, find maximum usable R_C (Ω).

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Correct answer: 22 to 23

Explanation

The base current is(5−0.7)/2000=2.15mA. In the assumed active model,Ic=100Ib=0.215A. At the supplied saturation boundary,Vce=0.2V,giving Rc=(5−0.2)/0.215=**22.326Ω**. Strict avoidance of this boundary requires a smaller resistance. The key uses Vce(sat),rather than the stricter collector-base reverse-bias condition Vc>Vb,which would limit Rc to20Ω.