Unsued op-amp half -> PS buffer?

[KarenColumbo]

I know someone gave me a hint about this some 2 years ago, but I can find neither post nor schematic.
I happen to have a half of an op-amp left in a BMP build. Some where I saw that it can be used i.e. to buffer Vb in a power supply as a unity gain buffer.
Like this, perhaps?

[Kipper4]

Yup Andreas that should work just fine.

[yanng45]

That will work indeed, if you're looking for real word examples both the Suhr Riot and the Friedman pedals use that setup iirc.

[KarenColumbo]

Thx guys - and in it goes

[bool]

But wasn't it already in in the first place?

[thetragichero]

this is what i do 👍

[marcelomd]

I like to use a buffer for volume control, maybe you can do that.

[R.G.]

Works great most of the time.

Be aware that it can also add mystery noise and feedback if you let any noise get into the bias divider that feeds the opamp. Be really picky about the filtering and grounding of the reference voltage feeding the opamp section to avoid this.

Also, for some opamps, you can't always simply use this to feed a decoupling capacitor to ground, or an array of capacitors to ground as you might otherwise do. Some opamps go unstable with high capactive loading, so you may need a small resistor, 10 to 100 ohms, after the opamp output but before the local decoupling caps on Vb.

[Rob Strand]

Be aware that it can also add mystery noise and feedback if you let any noise get into the bias divider that feeds the opamp. Be really picky about the filtering and grounding of the reference voltage feeding the opamp section to avoid this.

Also, for some opamps, you can't always simply use this to feed a decoupling capacitor to ground, or an array of capacitors to ground as you might otherwise do. Some opamps go unstable with high capactive loading, so you may need a small resistor, 10 to 100 ohms, after the opamp output but before the local decoupling caps on Vb.

+1

I guess my beef is by the time you add all the stuff to make it work *properly* you have a lot more components.  So you should really only use the opamp buffer *if* you really need it  ie. when you are
pulling so much current out of the VR (Vcc/2) rail that it would cause the rail to drop.  Otherwise there's
no advantage, just put a big cap there.  A 100uF cap will have a lower impedance than a 100R series resistor down to 20Hz or so.

[antonis]

IMHO, there is no need for R2/R3 high resistance values..
(10k/10k should also make it fine with less "noisy" proneness..)

[R.G.]

There is an article on picking bias voltage components at geofex, by the way.