I'm running a precision rectifier circuit on TL082. http://www.ti.com/lit/ds/symlink/tl082-n.pdf supplying dual supplies (+/-12V) has it working correctly, however a single supply(0-12V) does not. I'm guessing that the asymmetrical supply has ground at midrail, or 6v. However, offsetting the input does not correct behaviour. I'm sure there is something simple I don't understand here. circuit


1 Answer 1


Every time you take the input voltage higher than 0V you are "asking" the op-amp to produce a negative output voltage - this circuit is an inverting precision rectifier - it is trying to make a negative voltage on the output follow the positive voltage on the input. With no negative supply it doesn't work. With a positive bias and no negative supply it doesn't work.

Try a negative bias on the input or a positive bias on the non-inverting input.

Alternatively swap the diode directions and let a positive rectified output from the op-amp properly follow a negative half cycle on the input.

  • \$\begingroup\$ Thanks for the explanation Andy. I would like the input and output to be biased at ground. Would I be able to buy a "dual supply wallwart"? I've read about creating dual supplies with a single supply, however stable circuits are quite time consuming to build. \$\endgroup\$
    – nvctus
    Nov 13, 2015 at 13:26
  • \$\begingroup\$ I can't say if a dual wall wart is available - I guess there should be some around. Alterntively you can get away with a rail-to-rail op-amp providing the input frequency is low: cds.linear.com/image/456_circuit_1.jpg \$\endgroup\$
    – Andy aka
    Nov 13, 2015 at 14:40

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