# GATE Papers >> ECE >> 2017 >> Question No 39

Question No. 39

In the figure shown, the npn transistor acts as a switch.

For the input Vin(t) as shown in figure, the transistor switches between the cut-off and saturation regions of operation, when T is large. Assume collector-to-emitter voltage at saturation VCE(sat)=0.2V and base-to-emitter voltage VBE(sat)=0.7V. The minimum value of the common-base current gain($\alpha$) of the transistor for the switching should be___________.