# Electronic Devices and Circuits Questions and Answers – Rectifiers

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Rectifiers”.

1. The diode rectifier works well enough if the supply voltage is much than greater than 0.7V. For smaller voltage (of few hundreds of millivolt) input which of the following can be used?
a) Superdiode
b) Peak rectifier
c) Precision rectifier
d) None of the mentioned

Explanation: Super diodes are utilised for supply voltages less than 0.7V.
2. A simple diode rectifier has ‘ripples’ in the output wave which makes it unsuitable as a DC source. To overcome this one can use
a) A capacitor in series with a the load resistance
b) A capacitor in parallel to the load resistance
c) Both of the mentioned situations will work
d) None of the mentioned situations will work

Explanation: When a capacitor is connected in series with a resistor, it can only reduce waves. Once the capacitor is fully charged, the series connection will become an open circuit.
33. Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kΩ. Calculate the fraction of the cycle during which the diode is conducting
a) 1.06 %
b) 2.12 %
c) 3.18%
d) 4.24%

Explanation: w Δt ~ √(2Vr/Vp)
Θ = √(2 X 2/100)
Θ = 0.2 rad or 3.18% of the cycle

(Q.9-Q.10) The op amp in the precision rectifier circuit is ideal with output saturation levels of ±12 V. Assume that when conducting the diode exhibits a constant voltage drop of 0.7 V. 4. Find V– when VI is -1V.
a) 0V
b) 0.7V
c) 1V
d) 1.7V

Explanation: VI = -1v
Vo = 1v
VA = 1.7v
V– = 0v
Virtual gnd as negative feedback is closed through R.
VI > 0 D1 conducts D2 cutoff.
VI < 0 D2 conducts D1 cutoff.
V0 ⁄ VI = -1. 5. Find V0 when VI is 2V.
a) 0V
b) 0.7V
c) 1V
d) 1.7V

Explanation: VI = 2v
Vo = 0v
VA = -0.7v
V– = 0v
Virtual gnd as negative feedback is closed through R.
VI > 0 D1 conducts D2 cutoff.
VI < 0 D2 conducts D1 cutoff.
V0 ⁄ VI = -1. 6. Which of the following isn’t a type of rectifier?
a) Precision Half-wave Rectifier
b) Bridge Rectifier
c) Peak Rectifier
d) None of the mentioned

Explanation: All of the aforementioned types of rectifiers are different.
7. For a half wave or full wave rectifier the Peak Inverse Voltage of the rectifier is always
a) Greater than the input voltage
b) Smaller than the input voltage
c) Equal to the input voltage
d) Greater than the input voltage for full wave rectifier and smaller for the half wave rectifier

Explanation: Due to the existence of a diode, the peak input voltage is lower than the input voltage (s). A single diode lowers the output voltage by about 0.7 volts.
8. For a half-wave rectifier having diode voltage VD and supply input of VI, the diode conducts for π – 2Θ, where Θ is given by
a) tan -1 VD/VI
b) tan-1 VD/VI – VI
c) sin-1 VD/VI
d) sin-1 VD/VI – VI

Explanation: When VD VI, the diode does not conduct. As a result, = sin-1 (D/VI).
9. Bridge rectifier is an alternative for
a) Full wave rectifier
b) Peak rectifier
c) Half wave rectifier
d) None of the mentioned

Explanation: In comparison to a full wave rectifier, a bridge rectifier is a preferable option.
10. Which of the following is true for a bridge rectifier?
a) The peak inverse voltage or PIV for the bridge rectifier is lower when compared to an identical center tapped rectifier
b) The output voltage for the center tapped rectifier is lower than the identical bridge rectifier
c) A transistor of higher number of coil is required for center tapped rectifier than the identical bridge rectifier
d) All of the mentioned

Explanation: For a bridge rectifier, all of the above are correct.

A rectifier is an electrical device that transforms electromagnetic (AC), which reverses direction on a regular basis, to direct current (DC), which only flows in one direction. The inverter performs the reversing process. The procedure is known as rectifying because it “straightens” the current course. Vacuum tube diodes, wet chemical cells, mercury-arc valves, stacks of copper and selenium oxide plates, semiconductor diodes, silicon-controlled rectifiers, and other silicon-based semiconductor switches are all examples of rectifiers. Even synchronized electromechanical switches and motors have been employed in the past.