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Some time ago I posted a PSU with TL071 op amps 0-30V 0-3A, but It had some downsides, I could not get rid off. For instance, TL071 has an output that is around 2-3V below the supply rails. Adding to that, a 1-2V drop to drive the transistors, and 0.3V for the current sense resistor, we are looking at 5-6V supply rail above the output. That's 36V - right at the edge of TL071. This is already a risky place for the op amps, and on top of that - TL071 can only get 2V above its ground pin. That means it doesn't drive the output down to 0V as well. The whole thing was very problematic.
The solution - take the stress off the op amps. In this example, you can actually drive the PSU at much higher voltages, and currents, without the negative effects the op amps are subjected to. A low gain, closed loop amplifier stage is added to the op amp, so that It acts as a level shifter, and can drive the output well enough. The op amps can be MCP601's which are rail to rail with supply voltage of 5-6V only. The rest is pretty much the same concept as my previous circuit.
It should be easy enough to integrate a switching preregulator to keep the losses low. Might research on that for a future version
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