Instructions:
- The marks are indicated in the right-hand margin.
- There are NINE questions in this paper.
- Attempt FIVE questions in all.
- Question No. 1 is compulsory.
Q.1 Choose the correct option/answer the following (Any seven questions only):[2×7=14]
-
For a half-wave rectifier, if the peak secondary voltage is 20 V, the average DC output voltage (ideal diode, no filter) is approximately
- 37 V
- 9 V
- 12.74 V
- 20 V
-
An inverting amplifier has R1 = 10 kΩ and Rf = 100 kΩ. The gain is
- 10
- 11
- −10
- −11
-
The maximum rectification efficiency of an ideal full-wave rectifier is approximately
- 40.6%
- 57.6%
- 81.2%
- 100%
-
A capacitor filter connected across load in a rectifier tends to
- Increase ripple content
- Decrease average output voltage
- Reduce ripple and smooth output
- Reverse the polarity
-
A JFET has IDSS = 10 mA, VP = −5 V. If ID = 3.6 mA, the approximate VGS is
- −1
- −3
- −2
- −4
-
For a BJT, which biasing method generally provides better thermal stability?
- Fixed bias
- Voltage divider bias
- Collector-to-base bias
- No bias
-
Compared to BJT, a FET generally has
- Lower input impedance
- Higher input impedance
- Zero output resistance
- No control terminal
-
In an intrinsic semiconductor, the number of free electrons is
- Greater than the number of holes
- Less than the number of holes
- Equal to the number of holes
- Zero
-
Which one of the following is a direct band-gap semiconductor commonly used in LEDs?
- Silicon
- Germanium
- Gallium Arsenide
- Carbon
-
In an n-channel enhancement MOSFET, drain current starts increasing significantly when
- VDS = 0 always
- VGS becomes more negative than threshold
- VGS exceeds threshold voltage
- Gate current becomes very large
Q.2 (a) Describe the enhancement-type MOSFET with a neat structure and explain why no channel exists at zero gate voltage.[7]
(b) What is an integrator circuit using an op-amp? Derive the output voltage equation and explain how it performs mathematical integration of the input signal.[7]
Q.3 (a) Convert the following numbers into: (i) (1230)4 = (....)10 (ii) (12.0625)10 = (....)2[7]
(b) For a JFET, IDSS = 8 mA, VP = −4 V. Determine the value of VGS when the drain current is 2 mA.[7]
Q.4 (a) Calculate the subtraction of the following decimal numbers using the 1's and 2's complement method. (i) 5250 − 321 (ii) 20 − 1000[7]
(b) Explain the difference between intrinsic and extrinsic semiconductors. Also compare n-type and p-type semiconductors with suitable energy band diagrams.[7]
Q.5 (a) Explain the breakdown mechanisms in a diode.[7]
(b) What is a clamper circuit? Explain the operation of a positive clamper and a negative clamper with waveforms.[7]
Q.6 (a) Explain the working and characteristics of a Zener diode. Why is it suitable for voltage regulation?[7]
(b) Explain the characteristics of a BJT in common collector configuration and compare it with CE and CB configurations.[7]
Q.7 (a) Explain the construction and working of a JFET.[7]
(b) Derive the expression for the gain of a non-inverting amplifier using ideal op-amp assumptions.[7]
Q.8 (a) Design a zero-crossing detector using an op-amp and draw its waveform.[7]
(b) Describe the operation of a center-tapped full-wave rectifier. Derive the expressions for output current, ripple factor, efficiency, and PIV.[7]
Q.9 Write short notes on any two of the following:[7×2=14]
- LED, photodiode and solar cell
- Zener diode as a voltage regulator
- Universal logic gates
- What are drift current and diffusion current in a p-n junction
