Q. No.Pure \(\mathrm{Si}\) at \(500~\text K\) has an equal number of electrons \((n_i)\) and the hole \((n_h)\) concentration of \(1.5\times10^{16}~\text{m}^{-3}.\) Doping by indium increases the hole concentration \(n_h\) to \(4.5\times 10^{22}~\text{m}^{-3}.\) The doped semiconductor is of:
1.
\(\mathrm{n}\text-\)type with electron concentration \(n_{e}=5\times10^{22}~\text{m}^{-3}\)
2.
\(\mathrm{p}\text-\)type with electron concentration \(n_{e}=2.5\times10^{23}~\text{m}^{-3}\)
3.
\(\mathrm{n}\text-\)type with electron concentration \(n_{e}=2.5\times10^{10}~\text{m}^{-3}\)
4.
\(\mathrm{p}\text-\)type with electron concentration \(n_{e}=5\times10^{9}~\text{m}^{-3}\)
A Zener diode, having breakdown voltage equal to \(15\) V, is used in a voltage regulator circuit, as shown in the figure. The current through the diode is:
1. \(10\) mA
2. \(15\) mA
3. \(20\) mA
4. \(5\) mA
For transistor action:
| (a) | the base, emitter and collector regions should have similar size and doping concentrations. |
| (b) | the base regions must be very thin and lightly doped. |
| (c) | the emitter-base junction is forward biased and the base-collector junction is reverse biased. |
| (d) | both the emitter-base junction as well as the base-collector junction are forward biased. |
Which of the following pairs of statements is correct?
1. (d) and (a)
2. (a) and (b)
3. (b) and (c)
4. (c) and (d)
| 1. | the current in the reverse biased condition is generally very small. |
| 2. | the current in the reverse biased condition is small but the forward-biased current is independent of the bias voltage. |
| 3. | the reverse-biased current is strongly dependent on the applied bias voltage. |
| 4. | the forward-biased current is very small in comparison to reverse-biased current. |
The electrical circuit used to get smooth output from a rectifier circuit is called:
1. oscillator.
2. filter.
3. amplifier.
4. logic gates.
| 1. | In the circuit (1) and (2) |
| 2. | In the circuit (2) and (3) |
| 3. | In the circuit (1) and (3) |
| 4. | Only in the circuit (1) |
The emitter-base junction of a transistor is …… biased while the collector-base junction is ……. biased.
1. reverse, forward
2. reverse, reverse
3. forward, forward
4. forward, reverse
For a transistor, the current amplification factor is 0.8 when it is connected in the common base configuration. The transistor is now connected in common emitter configuration. The change in the collector current when the base current changes by 6 mA, is:
1. 6 mA
2. 4.8 mA
3. 24 mA
4. 8 mA
Consider an NPN transistor amplifier in the common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?
1. 1.1 mA
2. 1.01 mA
3. 0.01 mA
4. 10 mA
© 2026 GoodEd Technologies Pvt. Ltd.