Hi,
I'm reading a book about OpAmps and simulating the exercises with LTSpice. Here's the exercise and circuit i'm working with:
Using the basic 741 model (circuit below) direct PSpice to find the closed-loop parameters (Voltage Gain, Input resistance and output resistance) of an inverting amplifier implemented with R1=1k and R2 = 100k.
The circuit on the book:
The circuit built in LTSpice (i have not PSpice so i'm using LTSpice):
The results based on a Ideal OpAmp are:
Voltage Gain = -R4/R3 = -100k/1k = -100
Input resistance = R3 = 1k
Output resistance = 0
Results according to the book:
Voltage gain = -9.995E+01
Input resistance = 1.001E+03
Output resistance = 3.787E-02
To get the results on the simulation i run an AC Analysis and plot traces with algebraic expressions:
Voltage Gain: V(o)/V(i) = -99.949463 (Close to ideal)
Input resistance: V(i)/I(R3) = 1.0005004K (Close to ideal)
I don't know how to the output resistance
, i tried calculating V(o)/I(R2), but got ~100k, this isn't close to 0.
So my newbie question is how can i calculate the output resistance of the circuit?
Regards