I'm trying to do nodal analysis of a DC circuit that uses a mosfet and want to compare my results to what I would get using PSPICE....how do I do this?

If i was to remove the FET from the schematic what would I use to replace it for the circuit to behave the same (for the analysis). BTW the fet i'm using is a 2n7002.

Thanks in advance.

 

But where is the diagram?

 

Heres the diagram in a jpg, hope thats ok.

Also, this might be a seperate topic, but I'm not sure how I would calculate the rise time and the fall time at the load??

 

Is this a homework problem?

hgmjr

 

project i want to do to learn about fets. did not really cover them in my electronics class.

 

For your MOSFET circuit when the Micro 5V signal is in high state (5V).
You can treat MOSFET as a short circuit.
As long as the drain current does not exceed 75mA you can treat your MOSFET as switch with Ron = 3.5Ω.

And when the Micro 5V signal is in low state then you can remove the MOSFET form your circuit.

 

Thanks for the

When you treat it like a switch, do you need to consider the 5v from the micro? that was confusing me...

Also when I want to know the rise time and fall time do I use this equation:
V(t) = Vo*(1-(e^(t/T))

When I used this equation i got a rise time in nano-seconds, but pspice gave me a rise time in micro-seconds..i'm a bit lost about how to do this.

 

Thanks for the

When you treat it like a switch, do you need to consider the 5v from the micro? that was confusing me...

Yes, you can ignore the 5v from the micro.

Also when I want to know the rise time and fall time do I use this equation:
V(t) = Vo*(1-(e^(t/T))

Yes

When I used this equation i got a rise time in nano-seconds, but pspice gave me a rise time in micro-seconds..i'm a bit lost about how to do this.

Hmm, the rise time is defined as
tr ≈ 2.2RC
So for your circuit
tr ≈ 2.2* 770Ω*26nF ≈ 45μs for load
And Tr ≈ 2.2 *740Ω*13nF ≈ 22μs for ADC input.