Advertisements
Advertisements
प्रश्न
Consider an npn transistor with its base-emitter junction forward biased and collector base junction reverse biased. Which of the following statements are true?
- Electrons crossover from emitter to collector.
- Holes move from base to collector.
- Electrons move from emitter to base.
- Electrons from emitter move out of base without going to the collector.
पर्याय
d and a
a and b
b and c
a and c
Advertisements
उत्तर
a and c
Explanation:
Transistor: A junction transistor is formed by sandwiching 2 thin layer of P-type semiconductors between two N-type semiconductors. or by sandwiching a thin taver of V-type semiconductors between two P-type semiconductors.
E — Emitter (emits majority charge carriers)
C — Collects majority charge carriers
B — Base (provide proper interaction between E and C)
In normal operation base-emitter is forward biased, i.e., the positive pole of the emitter-base battery is connected to the base and its negative pole is connected to the emitter. And collector-base junction is reverse biased, i.e., the positive pole of the collector base battery is connected to the collector and the negative pole to base. Thus, electron moves from emitter to base and crossovers from emitter to collector.
APPEARS IN
संबंधित प्रश्न
(i) Explain with the help of a diagram the formation of depletion region and barrier potential in a pn junction.
What causes the setting up of high electric field even for small reverse bias voltage across the diode?
With reference to semiconductor devices, define a p-type semiconductor and a Zener diode.
Plot a graph showing variation of current versus voltage for the material GaAs ?
With reference to semi-conductors answer the following :
(i) What is the change in the resistance of the semi-conductor with increase in temperature ?
(ii) Name the majority charge carriers in n-type semi-conductor.
(iii) What is meant by doping ?
A plate current of 10 mA is obtained when 60 volts are applied across a diode tube. Assuming the Langmuir-Child relation \[i_p \infty V_p^{3/2}\] to hold, find the dynamic resistance rp in this operating condition.
The gain factor of an amplifier in increased from 10 to 12 as the load resistance is changed from 4 kΩ to 8 kΩ. Calculate (a) the amplification factor and (b) the plate resistance.
With reference to a semiconductor diode, what is meant by:
(i) Forward bias
(ii) Reverse bias
(iii) Depletion region
Diffusion in a p-n junction is due to ______.
We use alloys for making standard resistors because they have ____________.
The current through an ideal PN-junction shown in the following circuit diagram will be:
A – pn junction has a depletion layer of thickness .of the order of
The expected energy of the electron at absolute zero is called:-
In a semiconductor diode, the barrier potential offers opposition to only
The breakdown in a reverse biased p–n junction diode is more likely to occur due to ______.
- large velocity of the minority charge carriers if the doping concentration is small.
- large velocity of the minority charge carriers if the doping concentration is large.
- strong electric field in a depletion region if the doping concentration is small.
- strong electric field in the depletion region if the doping concentration is large.
Consider a box with three terminals on top of it as shown in figure (a):
 (a) |
Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement. A student performs an experiment in which any two of these three terminals are connected in the circuit shown in figure (b).
 (b) |
The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit. The graphs are
(i) when A is positive and B is negative
 (c) |
(ii) when A is negative and B is positive
 (d) |
(iii) When B is negative and C is positive
|
(e) |
(iv) When B is positive and C is negative
 (f) |
(v) When A is positive and C is negative
 (g) |
(vi) When A is negative and C is positive
 (h) |
From these graphs of current-voltage characteristics shown in figure (c) to (h), determine the arrangement of components between A, B and C.
The graph of potential barrier versus width of depletion region for an unbiased diode is shown in graph A. In comparison to A, graphs B and C are obtained after biasing the diode in different ways. Identify the type of biasing in B and C and justify your answer
| ‘A’ | ‘B’ | ‘C’ |
 |
 |
 |
Write the property of a junction diode which makes it suitable for rectification of ac voltages.
Read the following paragraph and answer the questions that follow.
| A semiconductor diode is basically a pn junction with metallic contacts provided at the ends for the application of an external voltage. It is a two-terminal device. When an external voltage is applied across a semiconductor diode such that the p-side is connected to the positive terminal of the battery and the n-side to the negative terminal, it is said to be forward-biased. When an external voltage is applied across the diode such that the n-side is positive and the p-side is negative, it is said to be reverse-biased. An ideal diode is one whose resistance in forward biasing is zero and the resistance is infinite in reverse biasing. When the diode is forward biased, it is found that beyond forward voltage called knee voltage, the conductivity is very high. When the biasing voltage is more than the knee voltage the potential barrier is overcome and the current increases rapidly with an increase in forward voltage. When the diode is reverse biased, the reverse bias voltage produces a very small current of about a few microamperes which almost remains constant with bias. This small current is a reverse saturation current. |
- In the given figure, a diode D is connected to an external resistance R = 100 Ω and an emf of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be:
(a) 40 mA
(b) 20 mA
(c) 35 mA
(d) 30 mA - In which of the following figures, the pn diode is reverse biased?
(a)
(b)
(c)
(d)
- Based on the V-I characteristics of the diode, we can classify the diode as:
(a) bilateral device
(b) ohmic device
(c) non-ohmic device
(d) passive element
OR
Two identical PN junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be:
(a) in the circuits (1) and (2)
(b) in the circuits (2) and (3)
(c) in the circuits (1) and (3)
(d) only in the circuit (1) 
The V-I characteristic of a diode is shown in the figure. The ratio of the resistance of the diode at I = 15 mA to the resistance at V = -10 V is
(a) 100
(b) 106
(c) 10
(d) 10-6
An ideal PN junction diode offers ______.
