Hello everyone.
I want to make a very low-noise linear power supply, 5 volts and up to 1 amp.
I've been thinking about integrated circuits like the LM78xx or LM317, but I'd rather put two or more in series to combine their ripple rejection and the low noise of both.
For example, an LM7812 followed by an LM7805.
Can the 70 dB ripple rejection of each be combined?
Just curious.
Regards.
I want to make a very low-noise linear power supply, 5 volts and up to 1 amp.
I've been thinking about integrated circuits like the LM78xx or LM317, but I'd rather put two or more in series to combine their ripple rejection and the low noise of both.
For example, an LM7812 followed by an LM7805.
Can the 70 dB ripple rejection of each be combined?
Just curious.
Regards.
To add to what Marcel mentions, 140db down on 5V is .5uV. At 1A, 1 milli-ohm of resistance in the layout gets 5mV or 60dB if I've done the math right. 140 will be very hard to achieve. Very.
Give it a try, both regulators can share the same heat sink, and you'll learn about proper layout practice.
That level of noise rejection is not needed for any home audio application. It's like asking for a drop forge when all you need is a tack hammer.