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Op Amp design for 1/2 gain

Deepen Solanki
Prodigy 30 points

Other Parts Discussed in Thread: OPA317

Hello. I need to design a circuit with the following specifications.

Input varies from 0-12V

For input varying from 0-10V, output should vary linearly from 0-5V.

For any input more than 10, output should get saturated at 5V.

I was thinking of using a general purpose amplifier with a gain of -0.5 and then a unity gain buffer with gain -1 and supply Vcc = 5 (to saturate output)

Will this work ? Also, what is the best Op Amp I could use to design this circuit ?


Thanks in advance :)

  • 0
    TI__Guru 64945 points

    Hi Deepen,

    Your design topology is one option, but to make sure that neither the input nor output voltage limitations are exceeded we recommend the simple circuit shown below.  A resistor divider is used to reduce the 0-12V signal to 0-4V.  The desired 0-10V input produces 0-3.3V. Therefore, a non-inverting amplifier with a gain of 1.5V/V is used to amplify the 3.3V signal to 5V.  Input signals over 3.3V (10V before the divider) will result in a saturated +5V output.  

    Please note that because the output is saturated for input signals above +3.3V, the op amp will display an overload recovery period after the input is reduced to within the usable 0-3.3V range.  This behavior is displayed in Figures 11 and 12 of the OPA317 product datasheet.

    Circuit.TSC