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
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    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
    16
    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
    7,050
    656
    Which way is the battery connected? Does the positive terminal connect to R1?
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    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.
    Please help.
    thanks

    Ken
     
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  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    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
    7,050
    656
    "Differential amplifier" is a BIG hint. Be creative. Use Google. You might learn the formula AND the derivation of it.
     
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