How do you find Vf and B, if a noninvtering amplifier has Ri of 1.0kOhm and an Rf of 100kOhm? V out is 5V?

Question

How do you find Vf and B, if a noninvtering amplifier has Ri of 1.0kOhm and an Rf of 100kOhm? V out is 5V?

Answer 1

I think 'B' is a typo. for 'G'

The formula for the gain of a non-inverting amplifier:

G = 1 + Rf/Ri

So, the Gain will be 1 + 100k/1k = 101

Vf, the voltage at the negative input to the amplifier will be the same as the positive input (less any small offset voltage).

Vf, the voltage across the feedback resistor will be:

Vout - Vout/101 = 5 - 5/101 = 4.95050505 volts (plus or minus the offset voltage of the amplifier, plus or minus the bias current * 1k)

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