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# Analog Electronics

1.

In a class C power amplifier the input signal has a frequency of 250 kHz. If the collector current pulses are 0.1 μs wide, the duty cycle of current waveform is

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2.

The open loop gain of an actual op-amp is about 100.

It is very high.

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3.

Negative feedback reduces noise originating at the amplifier input.

It has no effect on noise originating at amplifier input.

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4.

When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is

A high signal causes distortion because v-i characteristics of BJT is non-linear.

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5.

Which power amplifier can deliver maximum load power?

Since efficiency of class C operation is high, maximum load power is delivered.

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6.

Which of the following power amplifiers has highest efficiency?

Class C has more efficiency than all other classes.

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7.

A 12 kHz pulse wave-form is amplified by a circuit having an Upper cut-off frequency of 1 MHz. The minimum input pulse width that can be accurately reproduced is

tr = 10% Pω =   minimum Power(P) = 10 tr  10 x 0.35 μ sec = 3.5 μ sec.

Note: The I/P Pulse will be severely distorted if the rise time is more than 10% of Pulse width.

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8.

Assertion (A): In a full wave rectifier output the lowest ac component is at twice the input frequency

Reason (R): In a full wave rectifier, the output waveform consists of half sinusoids

Since output consists of half sinusoids, output frequency is twice the input frequency.

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9.

In a transistor E mode the collector current with the transistor in cut off region is

When transistor is cut off, IC is zero.

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10.

In a bridge rectifier circuit the rms value of input ac voltage is 10 V. The PIV across each diode is