HELP: what's happen about the OPA

[jake]

Hi all,
When I do the gain and phase simulations for an OPA, I encountered a strange issue. The gain of the second stage is minus. All the transistors are worked in normal state, that is, they are in saturation state. The input signal is applied as the figure. The positive input IP is a 0.5V direct voltage, And the inductance and the capacitance are huge.
Who can help me?
Regards
jake

 

[terryssw]

I think it is better to state clearly the problems so that other can help you. From your information, I think the second stage has negative gain of course since it is an inverting CS amplifier.

 

[j2005]

I think it's because you've pumped in your AC signal through the negative input of your opamp. Anyway, this is a strange setup you have here..........

 

[jake]

Thanks for reply!
To j2005,
This simulation methods of OPA is useful one. I have solved the issue now. It's just a low-grade mistake. I mistake the scale of the transistor size, that is, I used the default vale meter as the scale of the transistor.