50-60 percent efficient chained ultra-high ripple rejection linear regulator

150

02:34:17

What do you do when your linear regulator’s output let’s through too much of the noise? Use it to power another linear regulator! Two -90dB linear regulators make a -180dB linear regulator which is probably more than anyone would need. The only disadvantage is inefficiency, but for low power loads that’s not an issue. Alternatively, you could use the regulator as a room heater if you need to power something big.

published 5 years ago

thebugger

5 years ago

At these attenuation levels, there is more noise that meets the eye. Thermal noise for starters, non-linear noise from the semiconductors as well. Another issue is that the regulator doesn't have a negative feedback - output becomes variable with the load. You should try an op amp for ripple suppression. Won't go as far as 100+dB, but anything above 70-80dB is somewhat of a waste (except in very specific circumstances)

jason9

5 years ago

Yeah, I’m aware of no negative feedback. It shouldn’t be a problem as long as multiple things aren’t using the power supply at once. Actually, the Early effect will negate a lot of the noise rejection due to the lack of negative feedback, so much so that it might just take this pairing of two PSUs to filter out the noise sufficiently (although that heavily depends on what’s considered sufficient) so negative feedback would actually be a good idea. Also, I could’ve easily used an OP-amp for strong negative feedback and ripple rejection, but that’s boring. It would be too simple to have any fun designing it, although creating a filter to create a good reference voltage for the OP-amp might be interesting.

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