op-amp gain and power

Discussion in 'General Electronics Chat' started by Blackbull, Sep 3, 2009.

  1. Blackbull

    Thread Starter Well-Known Member

    Jul 26, 2008
    70
    6
    Hi folks,
    I have a mV amplifier set for a gain of 10, it works very well, also I have a µV amplifier set for a gain of 100, this is sensitive to thermocouples etc. It occurred to me that if the 100 gain was reduced to 10 and the output fed to a second op-amp also configured to a gain of ten the total gain would be 100. The pointer to similar threads indicates that this is possible, but would this amplifier be as ‘’insensitive’’ as the 10 gain one? Would it be possible to power the second op-amp from the same regulators as the first? Any comments would be appreciated.
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Yes, this would be practical. The key to the circuits perfomance lies in the op amps themselves. Specific uses, such as thermocouples, are extra sensitive to certain performance specs, so high quality parts are a must. Of course, they cost more, performance costs. The op amps themselves must have good noise rejection, excellent DC offset characteristics, and thermal stability. Once you have a good power supply, the op amps are critical.
     
  3. Blackbull

    Thread Starter Well-Known Member

    Jul 26, 2008
    70
    6
    Thanks Bill, the op-amps I am using are superb, LT1050 CN8
    Blackbull
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    The method of cascading amplifiers to achieve the same gain is used when you need to achieve a wider bandwidth at the same gain. However, extra noise is added at each stage. In the case of a thermocouple I don't think you need to cascade two op amps, a single one can do the job with less additive noise.
     
  5. Blackbull

    Thread Starter Well-Known Member

    Jul 26, 2008
    70
    6
    And thanks Mik3 your comments are more helpful perhaps than you realise.
    Blackbull
     
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