[sdiy] Powering ICs from a Voltage Divider

[Needham, Alan]

Why not consider a simple zener regulator (with or without transistor
emitter follower), lower component count and no 'glitch' while power
cycling.
Even with the resistor divider, an emitter follower would be more
predictable than an op-amp.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Jerry
Gray-Eskue
Sent: 15 October 2009 13:21
To: Synth-diy at dropmix.xs4all.nl
Subject: FW: [sdiy] Powering ICs from a Voltage Divider



-----Original Message-----
From: Jerry Gray-Eskue [mailto:jerryge at cableone.net]
Sent: Thursday, October 15, 2009 7:20 AM
To: Justin Owen
Subject: RE: [sdiy] Powering ICs from a Voltage Divider


Good question,

I am looking at using a similar op amp supply voltage setup. The obvious
concern is current levels the op amp  can handle gracefully. The second
not
so obvious concern is whether you will get any power on/off  transients
while the circuit stabilizes. A third concern would be the stability of
the
voltage under varying load conditions, this would relate to how much
variation the load will have and slew rate of the voltage follower.

The first item, current level is easy to verify. The second is a
trickier
proposition, to be sure you may have to build it, put a storage scope on
it
and power cycle it several times to be sure. A bad transit could be a
show
stopping chip killer. Putting a largish cap 10 - 100 uf on the op amp
outputs to eat fast transits may be prudent.

- Jerry


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Justin Owen
Sent: Thursday, October 15, 2009 5:53 AM
To: SDIY List
Subject: [sdiy] Powering ICs from a Voltage Divider


Hello,

I have a circuit powered by an LM713 VReg, outputting 12V DC. I have an
optocoupler (6N138) that wants 5V VCC and a DAC (TLV5168) that I'm
(probably) going to power from 3V VCC.

Is there any reason why I shouldn't run two separate two
resistor/voltage
dividers from the 713, buffer each of them with an op-amp and power the
chips off of that?

Thanks

J


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