Hey all, this is just a super quick question regarding negative feedback and superposition.

The book was going over how to find the gain in terms of finite gain and feedback factor beta for some simple amplifier circuits but I am a bit confused in one of the steps they used for the inverting amplifier.

Solving for the non-inverting amplifier gain is easy because the the feedback voltage V- is a simple voltage division of the output, but it gets a bit trickier for the inverting amplifier.

What confuses me is that when they solve for the voltage V-, they use superposition:

\(V_{-} = V_{in}(\frac{R_{f}}{R_{in} + R_{f}}) + V_{out}(\frac{R_{in}}{R_{in} + R_{f}})\)

They do this by setting first Vin = 0 and solving for V- in terms of Vout, but then they set Vout = 0 and solve V- in terms of Vin...

I don't understand how they can set Vout = 0 if it is not an independent source. Can someone explain?

Thanks

Btw I am using the Microelectronic Circuits textbook by Jaeger and Blalock.

The book was going over how to find the gain in terms of finite gain and feedback factor beta for some simple amplifier circuits but I am a bit confused in one of the steps they used for the inverting amplifier.

Solving for the non-inverting amplifier gain is easy because the the feedback voltage V- is a simple voltage division of the output, but it gets a bit trickier for the inverting amplifier.

What confuses me is that when they solve for the voltage V-, they use superposition:

\(V_{-} = V_{in}(\frac{R_{f}}{R_{in} + R_{f}}) + V_{out}(\frac{R_{in}}{R_{in} + R_{f}})\)

They do this by setting first Vin = 0 and solving for V- in terms of Vout, but then they set Vout = 0 and solve V- in terms of Vin...

I don't understand how they can set Vout = 0 if it is not an independent source. Can someone explain?

Thanks

Btw I am using the Microelectronic Circuits textbook by Jaeger and Blalock.

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