MCQs on Analog Electronics

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01․ The base-emitter voltage of an ideal transistor is
0 V.
0.3 V.
0.7 V.
1 V.

Ideally, a saturated transistor acts as a closed switch contact between collector and emitter. Hence, there is no need of base emitter voltage to enable the transistor to work in active region. So, it is zero in the ideal transistor.

02․ In the active region, the collector current is not changed significantly by
base supply voltage.
base current.
current gain.
collector resistance.

Because, the collector resistance is constant at all time. So, that the collector current is not changed significantly by the collector resistance in the active region.

03․ The base-emitter voltage of the second approximation is
0 V.
0.3 V.
0.7 V.
1 V.

For the silicon transistor, the approximate normal operating voltage is 0.7 Volts. The operating voltage is nothing but the base emitter voltage.

04․ If the base resistor is open, what is the collect current?
0 mA.
1 mA.
2 mA.
10 mA.

If the base resistance is open, there is no path to flow the current from the source to the base of the transistor. Hence, the base current is 0 Amps.

05․ When the collector current increases, what does the current gain do?
Stays the same.
Any of the above.

The current gain is β = 1 / JC. Here, JC is collector current density. Hence, the value of current gain decreases or increases with respect to the collector current.

06․ The current gain of a transistor is defined as the ratio of the collector current to the
base current.
emitter current.
supply current.
collector current.

The current gain is represented by beta (β). It is approximately the ratio of the DC collector current to the DC base current in forward active region.

07․ The graph of current gain versus collector current indicates that the current gain
is constant.
varies slightly.
varies significantly.
equals the collector current divided by the base current.

Current gain varies slightly with respect to the collector current because, at one stage it achieves the saturation point. It says that how much current gain you we expect from the device.

08․ When the base resistor increases, the collector voltage will probably
stay the same.
all of the above.

If the resistance increases, then the voltage drop across resistance also increases. So, it does not provide the exact voltage to the load. Hence, according to that increase in collector resistance, we have to increase the collector voltage to provide the rated voltage to the load.

09․ If the base resistor is very small, the transistor will operate in the
cutoff region.
active region.
saturation region.
all of the above.

If the base resistance is very small, then the base current is very high. Since, we know that the base current is directly proportional to the collector current with the multiplying factor of current gain. So, the value of collector current is enormously getting high. In this time, the transistor operates in saturation region.

10․ Ignoring the bulk resistance of the collector diode, the collector-emitter saturation voltage is
a few tenths of a volt.
1 V.
supply voltage.

By ignoring the resistance of the collector diode, there can be a huge flow of collector current. It assumes direct short circuit in the transistor. Hence, in the short circuit condition, the collector emitter saturation voltage is zero always.