EASY
Earn 100

What is an oscillator? Draw the block diagram for oscillator.

Important Questions on Electronics and Communication

MEDIUM
An NPN transistor is used in common emitter configuration as an amplifier with 1 kΩ load resistance. Signal voltage of 10 mV is applied across the base-emitter. This produces a 3 mA change in the collector current and 15 μA  change in the base current of the amplifier. The input resistance and voltage gain are:
HARD
A realistic graph depicting the variation of the reciprocal of input resistance in an input characteristics measurement in a common emitter transistor configuration is :
MEDIUM
A common emitter amplifier circuit, built using an NPN transistor, is shown in the figure. Its dc current gain is 250RC=1  and VCC=10 V . The minimum base current for VCE to reach saturation is

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EASY
For transistor action, which of the following statements is correct?
MEDIUM

In the figure, given that VBB supply can vary from 0 to 5.0 V, VCC=5 V, βdc=200, RB=100 , RC=1  and VBE=1.0 V. The minimum base current and the input voltage at which the transistor will go to saturation, will be, respectively:

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MEDIUM

The output characteristics of a transistor is shown in the figure. When VCE is 10V and IC=4.0mA, then value of βac is 

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EASY
The ratio (R) of output resistance r0, and the input resistance ri in measurements of input and output characteristics of a transistor is typically in the range :
EASY
For a CE transistor amplifier the audio signal voltage across the collector resistance of 2kΩ is 2 V. The current amplification factor of the transistor is 100 . If the base resistance is 1kΩ, the input signal voltage and base current are respectively
MEDIUM

An n-p-n transistor has three leads A, B and C. Connecting B and C by moist fingers, A to the positive lead of an ammeter, and C to the negative lead of the ammeter, one finds large deflection. Then, A, B and C refer respectively to :

EASY
For a common emitter configuration, if α and β have their usual meanings, the correct relationship between α and β is:
MEDIUM

In the following common emitter circuit, β=100 and VCE=7 V. If VBE is negligible, then the base current is

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MEDIUM
What is an oscillator? Explain the use of transistor as oscillator under the following points: Labelled diagram of circuit 
HARD

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In the circuit shown, the value of β of the transistor is 48. If the supplied base current is 200 μA, what is the voltage at the terminal Y?

MEDIUM

The transfer characteristic curve of a transistor, having input and output resistance 100 Ω and 100 kΩ respectively, is shown in the figure. The voltage and power gain, are respectively:
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EASY
In a transistor circuit, the collector current is changed by 89 mA, if the emitter current is changed to 9.0 mA. The value of current amplification factor, β is
HARD
The dc common-emitter current gain of a N-P-N transistor is 50 . The potential difference applied across the collector and emitter of a transistor used in CE configuration is, VCE=2V. If the collector resistance, RC=4 KΩ, the base current IB and the collector current IC will be:
EASY
Let ie, ic and ib represent emitter current, collector current and the base current of a transistor, then
EASY
An unknown transistor needs to be identified as a npn or pnp type. A multimeter, with +ve and -ve terminals, is used to measure resistance between different terminals of transistor. If terminal 2 is the base of the transistor then which of the following is correct for a pnp transistor?
MEDIUM
Explain with the help of a labelled circuit diagram, the use of the transistor as an oscillator.
EASY
The positive feedback is required by an amplifier to act as an oscillator. The feedback here means