# One last one

Discussion in 'Homework Help' started by jamespierre, Dec 4, 2007.

1. ### jamespierre Thread Starter New Member

Dec 4, 2007
6
0
The input voltage to a certain op-amp inverting amplifier is 10 mV, and the output is 2 V. What is the closed-loop voltage gain?

2. ### Distort10n Active Member

Dec 25, 2006
429
1
Impossible. Unless the amplifier is pegging to the positive rail because of some nefarious reason.

Since it is inverting the output voltage would be -2V. An inverting amplifier has an ideal closed loop signal gain expressed as:

Vout/Vin = -Rf/Rg

You don't know the resistor values, but you know Vout and Vin so what is the gain?

3. ### RiJoRI Well-Known Member

Aug 15, 2007
536
26
"Gain" is the relationship between input and output -- in this case voltage. It is shown in a fractional form (Vo/Vi), which can usually be reduced. (If Vi = 5 and Vo = 10,Av = 2).

So, 2V/10mV will give you the gain: How much the signal has "gained" by passing through the amplifier.

(Now if only I had a "money amplifier"! )
--Rich

4. ### jamespierre Thread Starter New Member

Dec 4, 2007
6
0
That made perfect sense! You should be a professor haha