Feedback Amplifiers

The term (1+Aβ) is called as

• De-sensitivity

• Sensitivity

• Loop Gain

• None

Which of the following is correct with respect to transresistance amplifier?

• Output current is proportional to the signal current

• Output voltage is proportional to the signal current

• Output voltage is proportional to the signal voltage

• Output current is proportional to the signal voltage

The regenerative feedback amplifier overall gain is given by

• A_f = A/(1+Aβ)

• A_f = 1-Aβ

• A_f = A/(1-Aβ)

• A_f = 1+Aβ

When current feedback (negative) is applied to an amplifier, its output impedance....

• is decreased

• is increased

• remains the same

• none of the above

If A_v and A_f are the voltage gains of an amplifier without feedback and with negative feedback respectively, then feedback fraction is...

• (1/A_v) + (1/A_f)

• (1/A_v) - (1/A_f)

• (1/A_f) - (1/A_v)

• (A_v/A_f) - (1/A_v)

The essential conditions for sustained oscillation are

• |Aβ|=1 & ∠Aβ=0

• |Aβ<1 & ∠Aβ=0

• |Aβ|>1 & ∠Aβ=0

• |Aβ|<1 & ∠Aβ=180^o

A Hartley oscillator is used for generation of

• Very low-frequency oscillation

• Radio-frequency oscillation

• Microwave oscillation

• Audio-frequency oscillation

The gain of cascaded amplifier is equal to the

• Product of individual gains

• Sum of individuals gain

• Ratio of stage gains

• none of these

The degenerative feedback amplifier overall gain is given by

• A_f = A/(1+Aβ)

• A_f = 1+Aβ

• A_f = A/(1-Aβ)

• A_f = 1-Aβ

Identify the type of sampling and mixing in the following amplifier.

• Shunt/Voltage sampling, Series/Voltage mixing

• Series/Current sampling, Series/Voltage mixing

• Series/Current sampling, Shunt/Current mixing

• Shunt/Voltage sampling, Shunt/Current mixing