Voltage shunt feedback amplifier gain in MOS transistors

[SherlockBenedict]

I couldn't find out what would be the gain for this given circuit given the open loop gain of A_v




This is my guess

I can find that the loop gain Aβ is equal to g_mR_d which means that the closed loop gain should be

Av/ (1+g_mR_d) which is equal to g_mR_d/(1+g_mR_d) but if this is correct then

it looks as if R_f doesn't play any role at all.


I have one more doubt too. For a voltage shunt feedback amplifier we need to find out Rm which is the forward trans impedance gain but what will be the forward trans impedance gain for the above configuration? As no current could enter into a MOS device then how could you find that forward trans impedance gain? (Note that while finding this out feedback Rf is not taken into consideration).

 

[FvM]

The circuit doesn't make sense at all. A connected input voltage source shorts the feedback path. You may want to supplement the circuit by a second resistor to an inverting amplifier.

 

[crutschow]

That circuit will only have negative feedback if there is a resistance between Vin and the circuit input. Otherwise Vin shorts any feedback to AC ground, as FvM noted.