7805 vs switching voltage regulator noise comparison

Thread Starter

ege124

Joined Dec 4, 2016
3
Hi,
I have a simple question. Which would make less noise 7805 or a switching voltage regulator? Well, I think that it's probably 7805 as switching regulator needs to AC-DC conversion and there'll be some high-frequency AC noise. There may be some low noise models for switching regulators but for a generic model which is noisier? (--> in terms of grammar is this usage right?)
 

GopherT

Joined Nov 23, 2012
8,012
Hi,
I have a simple question. Which would make less noise 7805 or a switching voltage regulator? Well, I think that it's probably 7805 as switching regulator needs to AC-DC conversion and there'll be some high-frequency AC noise. There may be some low noise models for switching regulators but for a generic model which is noisier? (--> in terms of grammar is this usage right?)
LM7805 by far.
 

crutschow

Joined Mar 14, 2008
24,977
A 7805 will have microvolts of noise (as shown below) whereas most switchers will likely have several tens of millivolts of noise, thus the switcher is probably three orders of magnitude noisier than the 7805.
Of course that noise is likely only of concern if you are powering sensitive analog circuits.
upload_2017-9-10_23-16-6.png
 

Tonyr1084

Joined Sep 24, 2015
4,538
You ask two opposing questions. To answer yes or no won't give you enough information. So, the 7805 will produce less noise. When you asked again you asked which would produce more noise. You'll get more noise from a switching power supply.

A lot depends on what you're building. If noise is a critical factor and heat is not then I'd go with the 7805. But if heat is the critical factor then I'd go with the SMPS (Switch Mode Power Supply). If both heat and noise are critical factors I'd still go with the 7805 because you can dissipate the heat via a heatsink. Cleaning up noise would require more circuitry.

If you're using battery power then I'd opt for the SMPS as the 7805 will convert some of the battery energy into heat. You'll waste some power in the form of heat whereas a SMPS won't generate the same heat. However, I'm not real familiar with SMPS being battery powered. I suppose there could be a circumstance where you'd find such - but I'd be learning something if I were to learn that there IS a battery powered SMPS. I know BUCK converters are somewhat like an SMPS, maybe that potentially qualifies as a battery powered SMPS. The nice thing about a buck converter is that even when battery power runs low it can up-convert the voltage. But you can't get around the loss of power.
 
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