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I want to clamp a signal to positive voltages. Below is shown how clamping works in an inverting configuration. Is it possible to clamp in a non-inverting configuration without using a second op-amp (to invert the incoming signal) while avoiding the op-amp saturating?

enter image description here

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  • \$\begingroup\$ There are opamps which handle saturation very well, especially with a signal as slow as yours in the example. Would that be an option for you? \$\endgroup\$
    – winny
    Commented Feb 20, 2023 at 22:18
  • \$\begingroup\$ FWIW, I don't like the scheme for the inverting amp. You see circuits like that as parts of rectifiers, which is fine, but you need to ask yourself why are you clamping in the first place. Often, it's to prevent overvoltage at the input terminals. This circuit does that, but it can make the op amp sink an awful lot of current. \$\endgroup\$ Commented Feb 21, 2023 at 20:41
  • \$\begingroup\$ It's not used as part of a rectifier. It's part of an envelope follower where I want to make sure the output doesn't go below ground. \$\endgroup\$
    – Hansel
    Commented Feb 22, 2023 at 9:13

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You could just have your opamp not have a negative rail, so it can't go negative.

D1 (preferably Schottky) protects the non-inverting input from negative input voltages.

schematic

simulate this circuit – Schematic created using CircuitLab

A simple circuit that uses an opamp with bipolar supplies can be found from Wikipedia (precision rectifier), but it comes with the caveat that it is "not commonly used" because there's no feedback when input goes negative so opamp may ring when input comes back positive, reducing the frequency response of the circuit. But maybe that's OK in your application?

enter image description here

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  • \$\begingroup\$ Thanks for the suggestion. The reason I prefer not to go with a separate opamp that has its power connected to ground is that I have space constraints. I am using an OPA1678 in 3 mm x 3 mm QFN package for audio filtering purposes and would prefer to use two of the remaining opamps that I have left over in this package. That's more space saving than using two separate packages with 2x opamps each (besides the fact that the OPA1679 is hard to come by given the situation in the market). \$\endgroup\$
    – Hansel
    Commented Feb 21, 2023 at 16:32
  • \$\begingroup\$ OK, added a 2nd circuit that can use bipolar supplies. Please read the Wikipedia entry it came from ("Precision rectifier") to understand its limitations. \$\endgroup\$
    – td127
    Commented Feb 21, 2023 at 19:06

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