[SPICE] How to simulate an OTA?

[bobs911]

Hi, everyone:

I have one question about how to observe the Gm of a OTA for continuous filter.
It differs from the voltage-mode opamp.

I want to observe the relationship between the output current and input voltage, that is, transconductance Gm.
But I don't know how to write the testbench/command/parameter to extract the output current in the simulator - hspice. :|
Even with the loading such as a cap, there is no output current in the output node.

Can anyone answer me the question by taking a simple single-ended amplifier for example or write the spice command for me?

Thank you for your explain!

 

[ipierre]

Generally, OTA Topology is like as Diff-Amp's

Av = B gm Ro

If you want to observe the output current,
It can be measured between PMOS and NMOS at output node.

I(OUTPUT) = I(PMOS)-I(NMOS)

Regards,
iPierre