Semiconductor Electronics: Materials, Devices and Simple Circuits

If a p-n junction diode of depletion layer width W and barrier height V₀ is forward biased, then

• W increases, V₀ decreases

• W decreases, V₀ increases

• both W and V₀ increase

• both W and V₀ decrease

The heavily and lightly doped regions of a bipolar junction transistor are respectively

• base and emitter

• base and collector

• emitter and base

• collector and emitter

The circuit diagram shows a logic combination with the states of outputs X, Y and Z given for inputs P, Q, R and S all at state 1. When inputs P and R change to state 0 with inputs Q and S still at 1, the states of outputs X, Y and Z change to

• 1, 0, 0

• 1, 1, 1

• 0, 1, 0

• 0, 0, 1

In a common emitter transistor amplifier, the output resistance is 500 kΩ and the current gain β = 49. If the power gain of the amplifier is 5 x 10⁶, the input resistance is

• 325 Ω

• 165 Ω

• 240 Ω

• 225 Ω

In the circuit given the current through the zener diode is

• 10 mA

• 6.67 mA

• 5 mA

• 3.33 mA

A transistor oscillator is

(i)  an amplifier with positive feedback 

(ii)  an amplifier with reduced gain 

(iii) the one in which DC supply energy is converted into AC output energy. Then 

• All (i), (ii) and (iii) are correct

• (i) and (ii) are correct

• (i) and (iii) are correct

• (ii) and (iii) are correct

A pure semiconductor has equal electron and hole concentration of 1O¹⁶ m^-3. Doping by indium increases n_h to 5 x 10²² m^-3. Then, the value of n_e in the doped semiconductor is

• 10⁶ /m³

• 10²² /m³

• 2 × 10⁹ / m³

• 10¹⁹ /m³

The collector supply voltage is 6 V and the voltage drop across a resistor of 6OO Ω in the collector circuit is 0.6 V, in a transistor connected in common emitter mode. If the current gain is 20, the base current is

• 0.25 mA

• 0.05 mA

• 0.12 mA

• 0.02 mA

A full-wave rectifier circuit with an AC input is shown

The output voltage across R_L is represented as

The truth table for the following logic circuit is

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 0\\ 0& 1& 1\\ 1& 0& 1\\ 1& 1& 0\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 0\\ 0& 1& 1\\ 1& 0& 1\\ 1& 1& 1\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 1\\ 0& 1& 0\\ 1& 0& 1\\ 1& 1& 0\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 1\\ 0& 1& 1\\ 1& 0& 0\\ 1& 1& 1\end{array}\right|$