Create Negative reference voltage using Op-Amp

Discussion in 'The Projects Forum' started by CR2504life, Jul 17, 2011.

  1. CR2504life

    Thread Starter New Member

    Feb 26, 2010
    I need to create a negative high voltage reference voltage (-80V), I think the attached circuit will do the job.

    It uses a precision +5V reference, and a high voltage op-amp in the inverting configuration to produce -80V output. The op-amp can handle +/-50V or 100V rail supply voltages. Im thinking of using unbalanced supply voltages of +10/-90V so the the output can reach -80V.

    Does anyone have a reason that this might not work ? or have any better ideas ? I hope that the circuit will have very little voltage drift, it doent need to sink/source much current.

    Thanks for your help.
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    I just had a look at the datasheet and clearly says:
    "Some applications do not require equal positive and negative output voltage swing. Power-supply voltages do not need to be equal. The OPA454 can operate with as little as 10V between the supplies and with up
    to 100V between the supplies. For example, the positive supply could be set to 90V with the negative supply at – 10V, or vice-versa (as long as the total is less than or equal to 100V)."

    So I think it should be ok.
  3. SgtWookie


    Jul 17, 2007
    Consider using a 10k resistor on the input and 160k for feedback instead of 1k/16k. If you keep the values you're using now, you'll need to use a 1 Watt for the 16k resistor, and the opamp will be dissipating over 400mW power just keeping 5mA current flowing through it, and another 25mW for the 1k resistor.

    Use metal film resistors for reduced noise and increased stability. 1/10 Watt will be fine for the 160k.
    Last edited: Jul 17, 2011