MOSFET equivalent rsistance

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I'm designing a photon counting circuit using PSpice and I'm replacing
a 100k resistor with a mosfet but first need to get the equivalent
resistance of the mosfet. Can anybody tell me how to do this?

Thanks.

 

[Jim Thompson]

I'm designing a photon counting circuit using PSpice and I'm replacing
a 100k resistor with a mosfet but first need to get the equivalent
resistance of the mosfet. Can anybody tell me how to do this?

Thanks.

Simulate it ?

...Jim Thompson

 

[daceo]

Simulate it ?

If you are trying to use it as a current source, the thread "is a
mosfet really a good current source" may be interesting, (but
strangely truncated now???) It is quite good to make up /use a curve
tracer and then measure the dV and dI. Some mosfets are better than
others, avoid ST! the parameter lambda is used to determine the drain
impedance with respect to current, but the models in switcher cad all
seemed better than real devices in this respect to me.

daceo

 

[Robert Baer]

I'm designing a photon counting circuit using PSpice and I'm replacing
a 100k resistor with a mosfet but first need to get the equivalent
resistance of the mosfet. Can anybody tell me how to do this?

Thanks.

You say nothing about biasing of the FET, source current, regular
power FET, logic FET, etc & etc.
So the answer is: the resistance can be anything from about 30
milliohms to kmegohms (or more).