MCQs on Analog Electronics

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01․ Depending upon the switching recovery time and on state drop, the power diodes are types
General purpose, fast recovery.
Fast recovery, Schottky.
General purpose, fast recovery and schottly.
None of these.

Power diodes are classified according to their reverse switching recovery characteristic. The three types of power diodes are as under - general purpose diodes (high reverse recovery time), fast recovery (low reverse recovery time) and schottky diodes.
02․ The trapped energy of an inductive load can be feed back to the input supply through a diode known as
Zener diode.
Feed back diode.
Powe diode.
None of these.

A diode which provide a return path for current back supply is know as feed back diode. These diodes also help in preventing the load voltage from increasing towards no load. The feed back diodes conduct when the voltage and current are of opposite polarity.
03․ A schottky device is a
Fast recovery device.
Minority carrier device.
Majority carrier device.
Both B and C.

Since in forward bias operation of schottky diode, the eletrons on the N side gain enough energy to cross the junction and plunge into the metal with very large energy, they are usually majority carrier.
04․ Optocouplers combine
IGBTs and MOSFETs.
SITs and BJTs.
Power transistor and silicon transistor.
Infrared light emitting diode and a silicon photo transistor.

Optocoupler is a device that contains an infrared LED and a photodetector (such as a photodiode, photo transistor, SCR or TRIAC, Darlington pair) combined in a package.
05․ Single phase, 230 V, 1 KW heater is connected acrose single phase 230 V, 50 Hz supply through a diode. The power delivered to the heater element
100 W.
1000 W.
500 W.
None of above.

Resistance of heater R = 2302/1000 = 52.9 Ω. Now, Vm = 230√2 Vor = Vor2/R = 500 W.
06․ For a diode, reverse recovery time is defined as the time between the instant diode current becomes zero and the instant reverse recovery current decays to
0.
10% of reverse peak current.
25% of reverse peak current.
15% of reverse peak current.

The reverse recovery time is defined as the time between the instant forward diode current becomes zero and the instant reverse recovery current decays to 25% of its reverse peak value of current.
07․ Reverse recovery current in a diode depends upon
PIV.
Temperature.
Storage change.
Forward field current.

In a diode, reverse recovery current and storage charge depends on the forward current of the device.
08․ The softness factor for soft recovery and fast recovery diodes are respectively
1, 1.
1, >1.
<1, 1.
1, <1.

The ratio of time interval from maximum reverse recovery current to 25% of revese peak current to time interval between zero crossing of the diode current to reach reverse peak current is called softness factor of diode. A diode with softness factor equal to 1 is called soft recovery and with softness factor less than 1 is called fast recovery.
09․ Peak inverse voltage (PIV) can be termed as
Reverse saturation voltage.
Zener break down voltage.
Peak repetitive voltage.
Advalance break down village.

Peak inverse voltage is the maximum voltage that can be applied to the P-N junction without damage to the junction. If the reverse voltage across the junction exceeds its peak inverse voltage, the junction may get destroyed owing to exessive heat.
10․ MOSFET requires
A large input current.
Only small input current.
A large input current and high voltage.
None of these.

A MOSFET is a voltage controlled device and requires only a small input current. This is because of the fact that gate circuit impedence in MOSFET is extremly high, of the order of 109 ohm.
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