# What will be small signal trans resistance gain of shown circuit?

Take beta = 99.

I analysed this circuit using first considering this circuit as feedback circuit with shunt-shunt type of feedback and then did the same analysis considering that the circuit is a common emitter amplifier ; i.e. I pretended that I don't know feedback circuits and followed the basic approach of nodal analysis followed in small signal analysis.

I got different results for small signal Voltage gain from both type of analysis. Obviously, the analysis without considering the network as feed back is correct, but I want to ask that how to realize that I should solve using basic approach neglecting feedback concepts.

I am having vibe that it has to do something with approximations taken while feedback analysis that

[Y12]A<<[Y12]B

[Y21]A>>[Y21]B

are not appropriately satisfied in below circuit. That is why I got different answers. Please clear up this concept. My calculations for Voltage gain

For calculating trans resistance gain

Why I am getting different answers for trans resistance gain using different approach?

• The gain will be around $A_V \approx gm*RC \approx 0.28S*510\Omega \approx 143 V/V$
– G36
Jun 18, 2019 at 13:48
• @G36 I am also getting the same answer by small signal analysis but after doing analysis considering circuit as an example of shunt-shunt feedback topology I get 74 as voltage gain.I am having problem in understanding that why there is so much difference in result. Jun 18, 2019 at 13:56
• Your, feedback analysis is wrong. Because Vin (ideal voltage source) will kill the feedback effect.
– G36
Jun 18, 2019 at 14:05
• @G36 thanks for pointing out but I am also getting different answers when i calculate trans resistance gain using two approach see edited Jun 18, 2019 at 14:42