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I'm designing a full-wave precision rectifier using OP07 in LTSpice. The first stage of the circuit (shown below) buffers the AC input using an OP07.

Schematic

But the buffer output is clipped with a significant DC offset at 10 V input when the peak of the non-inverting terminal input is approximately 1.6 V: Buffer output for 10 V input

The buffer output is also clipped at 2 V input when the peak of the non-inverting terminal input is approximately 0.5 V, with the output waveform distorted: Buffer output for 2 V input

Both these non-inverting terminal voltages are below ±VDD. I observed a similar behavior on replacing the OP07 with the MAX4352.

Of course, the circuit with the OP07 replaced by a universal opamp - a single-pole opamp with no limits on output voltage swing - exactly buffers the input as expected, without any offset or clipping for both 10 V and 2 V inputs. Universal opamp buffer output for 10 V input

Why are MAX4352 and OP07 buffer outputs clipped and offset even though the non-inverting terminal voltage does not exceed ±VDD?

EDIT: As periblepsis and Andy aka pointed out, I messed up with the supply connections. The circuit now works as expected: enter image description here

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  • \$\begingroup\$ Isn't your +Vdd just 0 V? \$\endgroup\$ Sep 30 at 12:54
  • \$\begingroup\$ Ahh, indeed it is, I missed it somehow. \$\endgroup\$
    – Kartik
    Sep 30 at 13:10

1 Answer 1

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You have set-up your op-amp power supplies incorrectly. V2 positive is tied to ground and, of course V2 negative is at -12 volts but then, for V1, you have its negative terminal connected to -VDD when it should connect to ground: -

enter image description here

Alternatively leave as is but change V1's voltage to be 24 volts.

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  • \$\begingroup\$ Oh no, I missed checking the supply somehow. Thank you for pointing this out! \$\endgroup\$
    – Kartik
    Sep 30 at 13:08

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