Analog Electronics
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
Answer: C
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The open loop gain of an actual op-amp is about 100.
Answer: B
It is very high.
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Negative feedback reduces noise originating at the amplifier input.
Answer: B
It has no effect on noise originating at amplifier input.
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When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is
Answer: D
A high signal causes distortion because v-i characteristics of BJT is non-linear.
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Which power amplifier can deliver maximum load power?
Answer: D
Since efficiency of class C operation is high, maximum load power is delivered.
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Which of the following power amplifiers has highest efficiency?
Answer: D
Class C has more efficiency than all other classes.
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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
Answer: B
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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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
Answer: B
Since output consists of half sinusoids, output frequency is twice the input frequency.
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In a transistor E mode the collector current with the transistor in cut off region is
Answer: A
When transistor is cut off, IC is zero.
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In a bridge rectifier circuit the rms value of input ac voltage is 10 V. The PIV across each diode is
Answer: B
PIV is 2 x 10 = 14.14 V.
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