what kind of feedback for source degeneration?

[abcyin]

source degeneration analysis

Hi, all

I wanna know that what kind of feedback for source degeneration, voltage-voltage, current-voltage, voltage-current or current-current? anybody can figure it out for me, pls give a detailed explaination.

Thx in advance!

 

[Jim cage]

this is a series-series feedback : samples current - returns voltage.

 

[abcyin]

can you explain this in detail, or any literature on it is appreciated.

Thx again!

 

[Alex_IC]

You can understand this feedback with signal graf analisys

 

[sandeep_torgal]

You can understand this feedback with signal graf analisys

ANy documents to know more as to how to go about such analysis in a simpler way.

 

[Alex_IC]

Read this book.
Operational Amplifier Speed and Accuracy Improvement: Analog Circuit Design with Structural Methodology, Author: Vadim V. Ivanov Igor M. Filanovsky

You can find it in this forum. Hope this help you.

 

[yxo]

This is series-series or curent voltage topology. Output and input resistance are increasing.
betta = Vf/Io. Vf =Vsource.

Alex IC! Vd does not have effect on output current if we do not take into account channel length modulation. Also you have mistake in expression. Check units.

 

[Alex_IC]

Yes, there is a mistake, it is my fault..

But I am taking into account the channel length modulation

The right formula is Id=[Vref*gm+Vd/(R+r0)]/(gm*R+1)

 

[siddharthshukla]

i can suggest an easy method to find the kind of feedback employed in any circuit.Finding out the mixing is very easy:if the signal from the feedback path meets the input signal at a node then its current mixing,otherwise its voltage.finding out the type of sampling requires a little more effort. first short the output node and see whether the feedback signal vanishes or stays if it vanishes its voltage sampling. then u can open the output and see what happens to the feedback signal,if it vanishes its current sampling. Hope this helps