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I'm building a voltage supply that uses a DAC to convert a binary string into an analog voltage. The DAC can't source a lot of current, so I'm using unity-gain amplifiers after the DAC output on each channel. I want to make sure that those little unity-gain amplifiers don't get blown up in case the load is suddenly low resistance and draws a bunch of current (my little unity-gain amps can only handle 20 mA).

I was thinking about setting a sense resistor to produce a 0.7V voltage when the current reaches 20 mA, but I'm concerned that I'll be adding some noise to my output voltage (I'm going for low noise).

Is this the right way to go? Is there a discrete IC that is meant for this purpose that I should be using?

schematic

simulate this circuit – Schematic created using CircuitLab

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I don't understand how your circuit is supposed to work; especially the diode makes me frown... it will definitely not limit the current, on the contrary (it limits the voltage and even causes current if the output wants to go higher than 0.7V).

Anyhow:
The simplest solution is to use an OpAmp that is short circuit resistant by itself.

It is not unlikely that it already is the case (see datasheet).

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  • \$\begingroup\$ @nick_name Look for output short-circuit current or alike. \$\endgroup\$ – Golaž Aug 10 '15 at 13:13
  • \$\begingroup\$ @Golaž Thanks guys! I found that in the data sheet. One other question: I'm looking at the AD8244 quad buffer--the output current is sort of limited but it handles my supply rails (0-12V). Any recommendations on a quad-or-more buffer amp package that can pass those voltages with more than 20 mA? \$\endgroup\$ – nick_name Aug 10 '15 at 13:19
  • \$\begingroup\$ @nick_name: maybe the TLC274 satisfies your requirements \$\endgroup\$ – Curd Aug 10 '15 at 13:30

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