1
GATE ECE 2017 Set 1
Numerical
+2
-0
In the figure shown, the npn transistor acts as a switch.

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

2
GATE ECE 2017 Set 2
Numerical
+2
-0
In the circuit shown, transistors Q1 and Q2 are biased at a collector current of 2.6 mA. Assuming that transistor current gains are sufficiently large to assume collector current equal to emitter current and thermal voltage of 26m V, the magnitude of voltage gain Vo/Vs in the mid-band frequency range is _____________ (up to second decimal place).
3
GATE ECE 2015 Set 2
Numerical
+2
-0
In the ac equivalent circuit shown, the two BJTs are biased in active region and have identical parameters with β >> 1. The open circuit small signal voltage gain is approximately _______.
4
GATE ECE 2015 Set 1
Numerical
+2
-0
In the circuit shown, I1 = 80 mA and I2 b= 4mA. Transistors T1 and T2 are identical. Assume that the thermal voltage VT is 26 mV at 27oC. At 50oC, the value of the voltage V12 = V1 - V2 (in mV) is _______.