Op amp buffered power supply?

[matmonster58]

When ever a pedal needs an odd amount of opamps, the extra opamp is usually slapped on the end of the power supply.

For example, a pedal that uses 5 op amps would take 3 tl072s, that gives you 6 opamps to work with.

I usually see this extra op amp used as a unity gain buffer after the power filter caps. What benefit does this provide? Any noise on your power supply should also make it through the buffer. It seems to me the opamp buffer would only be limiting the current that your power section can supply.

 

[matmonster58]

Example from the ember boost/TC spar
Is the thought that the impedance at vref is very low so there isn't as much of your signal loss through the vref generator compared to an unbuffered voltage divider?

I'm thinking about it too hard and confusing myself

 

[jwin615]

There's a little isolation provided. It also smoothes a bit more. That's important for vref, particularly with some opamps. A little ripple in the power line won't necessarily be heard much but ripple on vref + amplified AC could cause your AC signal to get too close to the power rails.
That's by backwoods understanding anyway.

 

[Robert]

Buffering VREF also prevents loading the voltage divider down when a circuit has multiple VREF connections.

 

[JTEX]

^ This. Sometimes you just need a low impedance Vref. This means that it's able to supply (or sink) significant current without moving up or down with the load. A simple resistive divider made with sensible values, such as 100k or 10k, can't do this.