How to sweep dc input for differential circuit

[stanleyu]

Hi can anyone pls share how to sweep the DC input for a differential circuit.
I used a vcvs to convert a single input to a differntial signals. However, problem arise as the negative input will not turn on the other end of the amplifier.
WHat's the correct way to do it ?
I need to sweep this to get the differential output versus differential input curve and also the Gm of the differential pair.

Thanks for any valuable comments

 

[alphi]

1st: you need use double power(+/-/GND) for amplifier.
2nd:you need to adjust offset of amplifier.

 

[Fom]

I don't understand clearly what is your problem. Everything shoud be OK. Can you give schematic of your simulation?

 

[rfsystem]

use vcvs1 with 0.5 for positive input
use vcvs2 with -0.5 for negative input
connect both inputs of the vcvs1&2 to a vdc
sweep the voltage fo vdc

 

[guamak_menanak]

This problem is always occured when one or some of the transistor is off! So, make sure that all your transisitor is in saturation, not in linear or off region! This is to make sure to get your expected result!

One other thing, each time you sweep your dc voltage...make sure your transistors are all ON and saturation! :wink: