NMOS CS Amplifier PSpice Simulation Question

amplifiernmosspice

I have a rather peculiar question. I am attempting to recreate the circuit below (from one of my labs) of a Common-Source Amplifier design with a bypassed Source Resistance in PSpice. It has the following parameters:

R1 = R2 = 100k

Rd = 1k

Vsig = 100mV peak sinusoidal

f = 5kHz

enter image description here

So far so good. I have the circuit set up the same way as the figure. For my simulation profile, I just want to see the input and output waveforms for now. My question is:

What do I connect to the Coupling Capacitor at the Drain, where the figure shows Vout?

I tried connecting it to Ground and placing a Voltage Pin at the Capacitor which just gave me a 15V DC waveform. I am also told that I should not connect a Load Resistance across it. I'm pretty much stumped on what to connect there and where exactly I am measuring Vout across…

In all of my homeworks and textbook excercises, Vout has been taken across a load resistance connected between Drain and Ground (for a CS Amplifier with bypassed Rs).


Below is my PSpice Circuit and input/output waveforms after connecting a Load Resistance as suggested. For some reason I am seeing signal attenuation instead of amplification..
enter image description here
enter image description here

Best Answer

In Spice simulation you sometimes find that the simulation won't run unless there is something like a resistor in place so a node is not floating. You can insert a 10G resistor for a load and it will behave much like it was floating. Or do as Jim Thompson recommended on sci.electronic.design back on Sep 22, 2004:

Or edit the part pins such that "Float=R-to-GND", and PSpice will automatically place 1/gmin ohms to ground.

Or use a simulated scope probe like 10M in parallel with 10pF.