# finding the output voltage

Discussion in 'General Electronics Chat' started by superway, Aug 3, 2010.

1. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Hello,

Can anyone help me the fomulars how to find the output voltage Vo in the circuit below?

Thanks alot.

ken

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2. ### JDT Well-Known Member

Feb 12, 2009
658
86
Assuming that the 649k (R1, R2) resistors are always equal and the 200k resistors (R3, R4) are also always equal then the following formula applies:-

Vout = (V1-V2) 200k/649k

and the output voltage will theoretically be zero in your circuit because both inputs are at the same voltage. In practice, due to component tolerances and the op-amp input offset voltage it will not be exact.

3. ### timrobbins Active Member

Aug 29, 2009
318
18
What have you found out about the gain of an IA configuration?

What have you deduced about the range over which the output voltage can change?

Did rou want to identify the polarity of the input?

4. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Hi,

THe input voltage is 36vdc (batt. neg and batt. pos). Why is the purpose of Zenner Diode for?

Thanks

5. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
659
Which way is the battery connected? Does the positive terminal connect to R1?

6. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
659
You need to specify which input is V1 and which is V2. Your equation is correct if V1 connects to R2. Otherwise, you need a minus sign in front of it.

This equation does not include the zener.

7. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
Hi,

Here is the correct circuit. I need to caculate the Vout scale voltage.
thanks

Ken

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8. ### Ron H AAC Fanatic!

Apr 14, 2005
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659
The circuit is a differential amplifier, with a zener limiter added. The zener may not be conducting.

9. ### superway Thread Starter Active Member

Oct 19, 2009
128
0
How to find Vout scaled voltage? Which is the fomular?

Thanks

Ken

10. ### Ron H AAC Fanatic!

Apr 14, 2005
7,049
659
"Differential amplifier" is a BIG hint. Be creative. Use Google. You might learn the formula AND the derivation of it.