Are there any op-amps that are guaranteed to not have a sink at the output and only rely on the current consumption of the load to bring down the voltage when it needs to? Internally, an op-amp with a single push-only transistor at the output.

I'm asking as I have a semi-elaborate setup with virtual rails where the op-amps hang on to, wherein the output of the op-amps changes the float of this virtual rail. Hence, having a strong feedback mechanism. That and the op-amps always probing how to keep everything balanced, makes for a recipe for disaster. So I was hoping to find a few push-only op-amps to replace some to alleviate this oscillation problem.

  • 1
    \$\begingroup\$ Not that I know of, but presumably you could put a diode on the output (inside the feedback loop). Maybe another diode from output to input to prevent the op-amp from saturating when it's trying to pull current. \$\endgroup\$
    – John D
    Commented Sep 6, 2022 at 20:07
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    \$\begingroup\$ What's the output impedance of those "virtual rails"? If they're disrupted by the output current fluctuations of an op amp, that's a sign that the power supply rails suffer from too high output impedance. That's the root cause of the problem. I don't know of any IC manufacturers that have ever made a source-only opamp. There's no commercial demand for such a thing. \$\endgroup\$
    – MarkU
    Commented Sep 6, 2022 at 20:09

2 Answers 2


I've never seen any but it should be able to make one.


simulate this circuit – Schematic created using CircuitLab

Figure 1. A source-only unity-gain amplifier.

If VIN exceeds VOUT then OA1 will turn on Q1 which turns on Q2. The system will stabilise when VOUT = VIN.


I was hoping to find a few push-only op-amps to replace some to alleviate this oscillation problem.

It will just oscillate at a lower frequency then. After all, the op-amps will still try to work - they'll just saturate, and then recover from saturation slowly. The oscillations will be nastier-looking, too.

Instead, load the op-amps with constant current sources. This will ensure that the op-amp output stage is biased into class-A operation.


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