1. For the BJT Q1 in the circuit shown below, β = ∞, VBEon = 0.7 Volts, VCEsat = 0.7 Volts. The switch is initially closed. At time t=0, the switch is opened. The time t at which Q1 leaves the active region is
2. In the circuit shown below, for the MOS transistors, µnCox = 100 µA/V2 and the threshold voltage VT = 1 volt. The voltage Vx at the source of the upper transistor is
3. For a BJT, the common – base current gain α = 0.98 and the collector base junction reverse bias saturation current Ico = 0.6µA. This BJT is connected in the common emitter mode and operated in the active region with a base drive current IB = 20 µA. The collector current IC for this mode of operation is
Common Data for Questions 4 and 5:
The channel resistance of an N-channel JFET shown in the figure below is 600 Ω when the full channel thickness (tch) of 10 µm is available for conduction. The built – in voltage of the gate P+N junction (Vbi) is -1 volt. When the gate to source voltage (VGS) is
0 volt, the channel is depleted by 1 µm on each side due to the built-in voltage and hence the thickness available for conduction is only 8 µm.
4. The channel resistance when VGS = 0 volts is
5. The channel resistance when VGS = - 3 volts is