Match the following lists : Codes :List – I List – II a. Voltage series feedback i. Trans resistance amplifier b. Current series feedback ii. Current shunt feedback c. Current amplifier iii. Trans-conductance d. Voltage shunt feedback iv. Voltage amplifier
a-iv, b-iii, c-ii, d-i
The name of each topology encodes the answer : the first word says what is sampled at the output, the second says how it is mixed at the input — series meaning in series (a voltage), shunt meaning in parallel (a current).
| Topology | Samples | Mixes | Amplifier type | Gain |
|---|---|---|---|---|
| a. Voltage series | Voltage | Voltage | iv. Voltage amplifier | Vo/Vi |
| b. Current series | Current | Voltage | iii. Transconductance | Io/Vi |
| c. Current amplifier | Current | Current | ii. Current shunt | Io/Ii |
| d. Voltage shunt | Voltage | Current | i. Transresistance | Vo/Ii |
So a-iv, b-iii, c-ii, d-i — option 3.
Reading the mixed entries. Items a, b and d name a topology and must be matched to an amplifier type; item c does the reverse, naming an amplifier type to be matched to a topology. Item c is therefore the easiest anchor: a current amplifier takes current in and gives current out, so it samples current and mixes current, which is current shunt feedback.
Item b is where mistakes are made. "Current series" means the output current is sampled while the feedback voltage is in series with the input — so the input variable is a voltage and the output a current. Gain therefore has the dimensions of conductance, giving a transconductance amplifier. The classic instance is an emitter resistor left unbypassed: it develops a voltage proportional to the output current and subtracts it from the base drive.
Item d is its dual. Voltage shunt feedback samples the output voltage and feeds current back into the input node — gain in ohms, hence transresistance. The inverting op-amp with a feedback resistor from output to virtual earth is exactly this, which is why the current-to-voltage converter is built that way.
What each topology does to impedance follows the same logic and is worth remembering together: series mixing raises input impedance, shunt mixing lowers it; voltage sampling lowers output impedance, current sampling raises it — each by the factor \(1+A\beta\). So voltage-series feedback gives the high input and low output impedance wanted of a voltage amplifier, and each topology is chosen for exactly this reason.
Hence, the correct match is a-iv, b-iii, c-ii, d-i.
Similar Questions
Match the following :
List – I List – II a. voltage shunt negative feedback i. increase of CMRR b. constant current source differential amplifier ii. O/P voltage attenuated by a factor 1/29 c. Phase shift oscillator iii. FSK decoder d. PLL iv. decrease of O/P impedance Codes :
Negative feedback in amplifier results in
1. reduced voltage gain
2. reduced bandwidth
3. increased S/N ratio
4. reduced distortionAn amplifier has open-loop voltage gain of 40. 10 % of negative feedback is effected. What will be the gain with feedback ?
Match List - I with List - II.
List - I (Feedback connection type) List - II (Input/output impedance) (A) Voltage series feedback (I) \(Z_{of}=\dfrac{Z_{o}}{1+\beta A}\) (B) Voltage shunt feedback (II) \(Z_{of}=Z_{o}\left(1+\beta A\right)\) (C) Current series feedback (III) \(Z_{if}=\dfrac{Z_{i}}{1+\beta A}\) (D) Current shunt feedback (IV) \(Z_{if}=Z_{i}\left(1+\beta A\right)\) Choose the correct answer from the options given below :
Given below are two statements :
Statement I : For negative feedback systems, the open loop gain decreases by a certain factor.
Statement II : Negative feedback systems are better in terms of system stability
In the light of the above statements, choose the correct answer from the options given below :
Negative Feedback in amplifiers :
(a) improves signal to noise ratio at the output
(b) increases distortion
(c) reduces input offset voltage
(d) increases bandwidth
Options :
Read the following statements :
(a) Whatever the mode of feedback be, the gain after negative feedback is \(\dfrac{A}{1+A\beta}\)
(b) A negative feedback reduces the bandwidth of the amplifier.
(c) A negative feedback increases the output impedance
(d) A negative feedback enhances the stability of operationWhich of the above statements are correct ?
Important Questions from Feedback Amplifier
The effect of negative feedback is to increase the __________ of a series voltage negative feedback amplifier by a factor of (1 + A vβ).
Which of the following improvement is obtained in negative feedback amplifier?
Feedback in an amplifier always helps to ________
What is the effect of current shunt feedback in an amplifier?
- The output impedance of a voltage series feedback is 10 Ω, If the gain of the basic amplifier is 100 and feedback fraction is 0.01, what is the output impedance without feedback?
