Is this output of folded cascode diff. amplifier correct?

[cjupiter]

correct output?

Here is my folded cascode fully diff amp without CMFB. I apply two sine waves, and i get output as shown. Even without the CMFB circuit, shouldnt i get a much larger voltage swing then the one i have achieved. If i should what could i be doing wrong. My W\L ratios correspond with Johns and Martins dimensions out of their book "Analog IC design" Any help much appreciated.

Thanks

-Con

 

[nxing]

correct output?

It's quite difficult to say what's the problem with your circuit. Which kind of technology you are using? you can not just copy one circuit between different technology. Also, you can check the operating point for every transistor to see whether or not they are operating at the approriate region.

Good Luck

 

[dumbfrog]

Re: correct output?

could you post the circuit
my first guess is that your bias was wrong, no current at all and the circuit has only leakage, result of tiny swing

for self debug purpose, trace back the signals to see where the signal starts to faded out.

 

[avinash]

Re: correct output?

check whether all of the transistors are operating in saturation region.