Question
Download Solution PDFIn a voltage series feedback amplifier, if Ri is the input resistance without feedback. then input resistance with feedback is:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
The comparison of different feedback configurations is as follows:
|
Parameter |
Voltage - Series |
Current - Series |
Current - Shunt |
Voltage-Shunt |
|
Input Resistance |
Increases \({R_{if}} = {R_i}\left( {1 + A\beta } \right)\) |
Increases \({R_{if}} = {R_i}\left( {1 + A\beta } \right)\) |
Decreases \({R_{if}} = \frac{{{R_i}}}{{1 + A\beta }}\) |
Decreases \({R_{if}} = \frac{{{R_i}}}{{1 + A\beta }}\) |
|
Output Resistance |
Decreases \({R_{if}} = \frac{{{R_i}}}{{1 + A\beta }}\) |
Increases \({R_{if}} = {R_i}\left( {1 + A\beta } \right)\) |
Increases \({R_{if}} = {R_i}\left( {1 + A\beta } \right)\) |
Decreases \({R_{if}} = \frac{{{R_i}}}{{1 + A\beta }}\) |
A voltage series feedback amplifier configuration is as shown:
\(\Rightarrow {Z_{in}}\left( {Input\;impedance} \right) = \frac{{{V_s}}}{{{I_s}}} = \frac{{{V_i} + {V_f}}}{{{I_s}}}\)
\(\Rightarrow \frac{{{V_i} + \beta {V_0}}}{{{I_s}}} = \frac{{{V_i} + \beta A{V_i}}}{{{I_s}}}\)
\( \Rightarrow {Z_{in}} = \frac{{{V_i}\left( {1 + \beta A} \right)}}{{{I_s}}} = {r_i}\left( {1 + \beta A} \right)\)Last updated on May 8, 2025
-> The KVS TGT Notiifcation 2025 will be released for 16661 vacancies.
-> The application dates will be announced along with the official notification.
-> Graduates with B.Ed or an equivalent qualification are eligible for this post.
-> Prepare with the KVS TGT Previous Year Papers here.