How to simulate a OTA with Hspice?

[adad3636]

dear all
I designed a OTA and i wanted to plot the "gm-Vin plot". When i wanted to simulate it using Hspice,i do not know what the output point should be connected,because it can't be floating! So i don't know how to measure the output current.

The output common mode voltage in my design is 1.65V.

Sorry, my english is poor.

 

[m.salehi]

u define gm in hspice by using
.print gm=par'.....'
then run hspice. in awanwaves apply vin as x axses, then plot gm in params.
if u have problem please contact me.
best regards.

 

[sigmadelta]

in ac analysis
.print av=par'vo/vin'
u can plot the magnitude-frequence of the av
how can i plot phase- frequenceof the av
thanks

 

[angelote]

It's a simulation. It isn't real world.
You can connect your OTA output to signal ground (for example) using a resistor. Calculate resistor's value to avoid OTA voltage saturation.