[sdiy] Powering ICs from a Voltage Divider

[Justin Owen]

> 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?

>> If your circuits are low enough currents to power from an op-amp why
>> not just add a TO-92 regulator?

Because I'm an impatient cheapskate? :) No - I still might. One thing that appealed to me about the op-amp idea is that I could use a trimmer to get an exact voltage - no having to worry about tolerances.

>>If your DAC is the TLV5618 and you run it at 3V your reference will
>>need to be around 1.2V or so. The TLV5618 has a voltage
>>doubler on the output. If you have 5V you may want to run the DAC off
>>of 5V. Of course if you only wanted a 2.5V span for
>>the 12bits then nevermind ;)

Exactly - 2.5 is the new 5. My circuit already scales 0-5V down by 50% anyway - getting the DAC to push 5 volts was just not necessary.

Cheers John.

Justin