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प्रश्न
With the help of neat labelled circuit diagram explain the working of half wave rectifier using semiconductor diode. Draw the input and output waveforms.
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उत्तर
A device which converts A.C. to D.C. is called rectifier. In this case output exists only for half cycle hence it is called half wave rectifier. Construction: The circuit diagram of a half wave rectifier using a junctiondiode is as shown in fig. The alternating voltage source is connected to the primary coil of a transformer. The secondary coil is connected to the diode in series with a resistance RL called the load resistance
T=Transformer
D=Diode
V0=output voltage
v1=input votage
RL=load resistance
Working: In first cycle of input voltage, the anode of the diode is positive potential w.r.t. cathode. Hence the diode is in forward-biased. Hence it conduct current. The current flows through load resistance giving voltage drop iRL. This voltage drop is called output voltage. During next half cycle the anode of diode is in negative potential w.r.t. Hence it is in reversed-biased. Hence it does not conduct the current. Hence current does not flow through load resistance giving no P.D. across it. Hence output voltage is unidirectional. It is called as D.C.
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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?
When a forward bias is applied to a p-n junction, it ______.
With reference to semiconductor devices, define a p-type semiconductor and a Zener diode.
Why is a zener diode considered as a special purpose semiconductor diode?
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 ?
The dynamic plate resistance of a triode value is 10 kΩ. Find the change in the plate current if the plate voltage is changed from 200 V to 220 V.
In semiconductor physics, what is meant by:
(i) rectifier
(ii) an amplifier
(iii) an oscillator
Basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc are ______.
Diffusion in a p-n junction is due to ______.
A – pn junction has a depletion layer of thickness .of the order of
The nature of binding for a crystal with alternate and evenly spaced positive and negatively ions is
In forward bias width of potential barrier in a p + n junction diode
In Figure, Vo is the potential barrier across a p-n junction, when no battery is connected across the junction ______.
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.
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.
Figure shows the transfer characteristics of a base biased CE transistor. Which of the following statements are true?
At Vi = 0.4 V, transistor is in active state.
At Vi = 1 V, it can be used as an amplifier.
At Vi = 0.5 V, it can be used as a switch turned off.
At Vi = 2.5 V, it can be used as a switch turned on.
In the depletion region of a diode ______.
- there are no mobile charges.
- equal number of holes and electrons exist, making the region neutral.
- recombination of holes and electrons has taken place.
- immobile charged ions exist.
 (a) |
 (b) |
- Name the type of a diode whose characteristics are shown in figure (A) and figure (B).
- What does the point P in figure (A) represent?
- What does the points P and Q in figure (B) represent?
A Zener of power rating 1 W is to be used as a voltage regulator. If zener has a breakdown of 5 V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of Rs for safe operation (Figure)?
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.
Draw V-I characteristics of a p-n Junction diode.
Explain the formation of the barrier potential in a p-n junction.
A semiconductor device is connected in series with a battery, an ammeter and a resistor. A current flows in the circuit. If. the polarity of the battery is reversed, the current in the circuit almost becomes zero. The device is a/an ______.
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 ______.
