Analog Circuits Questions and Answers Part-14

1. What is the value of DC equivalent output voltage for the given circuit, given that the input voltage is 20 Vp-p and 50 Hz and the diode is a silicon diode?
q131
a) 2.9574 V
b) -2.9574 V
c) -3.125 V
d) 0 V

Answer: b
Explanation: Vdc is given by 0.318(Vp). Here Vp = 10-0.7 V = 9.3 V and hence, Vdc = 0.318 x 9.3 V = 2.9574 V. Now, as the output Is non zero only for the negative half cycles of the input, Vdc = -2.9574 V.

2. Which of the following equations is correct for a full wave rectified output?
a) |Vdc| = 0.318 Vp
b) |Vdc| = 0.636 Vp
c) |Vdc| = 0.477 Vp
d) |Vdc| = 0.211 Vp

Answer: b
Explanation: The output dc level of a half wave rectified wave is equal to 0.318 Vp. But, for a fully rectified wave, it becomes equal to 0.636 of the peak value.

3. Which of the following statements are true about the given circuit?
q133
a) The circuit is that of a bridge rectifier
b) The PIV of the diode D1 must be greater than v0 for the circuit to function as a bridge rectifier
c) For silicon diodes, the value of v0=(vi-1.4) V
d) All of the mentioned

Answer: d
Explanation:The circuit is that of a bridge rectifier. For proper functioning, the PIV of diodes must be at least greater than v0 and since, the current through any path flows through 2 diodes. There is a drop of 1.4 V.

4. In the given circuit, what will be the nature of the output waveform?
q135
a) Half rectified
b) Full rectified
c) Sinusoidal
d) DC

Answer: b
Explanation: The right diode conducts during the positive half of the input cycle and the left diode conducts during the negative half of the input cycle. Hence, the output will be a fully rectified wave.

5. In the given circuit, what is the value of Vp for the output wave, if the input fed is 20 Vp-p?
q135
a) 10 V
b) 9.3 V
c) 5 V
d) 4.7 V

Answer: c
Explanation: As is clear from the circuit that v0 = 0.5 vi and hence peak value of the output wave is equal to half of the peak value of the input wave and hence Vp = 10/2 = 5 V.

6. From the given circuit, what is the value of current flowing through the 1 k resistor parallel to the diodes?
q136
a) 10 mA
b) 9.3 mA
c) 8.6 mA
d) 0 mA

Answer: a
Explanation: As both the diodes are reverse biased. Voltage drop across the resistor = 10 V. Hence, current = 10 V/1 k = 10 mA.

7. From the given circuit, what is the value of current flowing through the 1 k resistor?
q137
a) 0 mA
b) 10 mA
c) 9.3 mA
d) 0.7 mA

Answer: d
Explanation: As one of the diodes is forward biased, voltage drop across it = 0.7 V. Now, as this diode is in parallel with the given resistor, voltage across resistor = 0.7 V => current = 0.7 mA.

8. In the given circuit, what is the value of current flowing through the forward biased diode?
q138
a) 10 mA
b) 9.3 mA
c) 8.6 mA
d) 0 mA

Answer: c
Explanation: Here, current flowing through R2 = (10-0.7)/1k = 9.3 mA. Also the current through the parallel resistor=0.7 mA. Hence the current through the forward biased diode = (9.3-0.7) = 8.6 mA.

9. In the given circuit, what is the value of current flowing through the diode D2?
q139
a) 0 mA
b) 10 mA
c) 9.3 mA
d) 8.6 mA

Answer: a
Explanation: As the diode D2 is reverse biased, the current flowing through it = 0 mA.

10. In the given circuit, what is the value of the current through the series resistor R2?
q140
a) 9.3 mA
b) 10 mA
c) 0 mA
d) 8.6 mA

Answer: a
Explanation: The voltage across the diodes is 0.7 V as they are forward biased. Hence, the current through the series resistor = (10-0.7)/1k = 9.3 mA.