[Moved]Fully differential amplifier with CMFB

[gaurav5277]

can anybody help me understand this testbench.

 

[erikl]

I'd suggest to study the full test bench tutorial: View attachment Cadence_Characterizing_Differential_Amplifiers.pdf

 

[gaurav5277]

Hi,
Why and how is the second apmlifier ''acOpenDiff'' added?
I mean how do i use verilog A to do this?
Also please explain why is voltage sources at output of first amplifier added?

 

[erikl]

Why and how is the second apmlifier ''acOpenDiff'' added?

1. To not load the output of the 1^st amplifier additionally
2. To compensate for the DC-amplified offset

how is shown on the schematic.

Also please explain why is voltage sources at output of first amplifier added?

I think this is a replacement for a CMFB circuit, to keep the DC output voltage at the cmref level.