This one actually regulates thanks to a GNFB loop.
Some people dislike it, and go to great lenghts avoiding one, but I think it is harmless and bring objective benefits, like tighter regulation
Placing C2 there greatly reduces the ripple.
If ripple is not a major concern, you can use a single resistor and no cap
Translated in figures, the CCS version has a static line regulation of 11% and a static output resistance of 5.4 ohm.
The closed-loop version has a line regulation of 1.6% and an output resistance of 80 milliohm.
Dynamic figures are much better.
By contrast, passive dividers or non-stabilized CCS do far far worse
The closed-loop version has a line regulation of 1.6% and an output resistance of 80 milliohm.
Dynamic figures are much better.
By contrast, passive dividers or non-stabilized CCS do far far worse
I get more or less the same result wih and without.
I do get more ripple if removing C1 / R5.
I haven't seen these on other regulators.
What are they there for?
I suppose it has to do with M1 being the reference. An AC path for the gate?
I'm waiting for some parts, to be able to test in real life.
Looks like C1 is to feed ripple that may exist on the output into M1. R5 is likely a HF stopper. ?
If there is ripple on the output, M1 will modulate that ripple the opposite way, making M2 cancel the ripple.
If there is ripple on the output, M1 will modulate that ripple the opposite way, making M2 cancel the ripple.
Strange: without the cap, I get 2.5mV pp ripple, and with it, it falls to 115µV pp.
They bypass the feedback divider in AC, meaning the amplifier is connected in unity gain, thus maximizing the loop gain available to correct ripple, reduce output impedance, etc.
The main role of R5 is to reduce charge/discharge currents into D1 in case funny things are done at the output, like shorts, dumping, etc.
Secondarily it can also play the role of a stopper.
If you are interested, in the Tubes section, I have given an example of LDO regulator (negative)
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