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I've been looking at DACs on Digikey and other electronics sites in hopes of finding a circuit to drive > 20 electrical nodes with ~10 mA per channel, 0->8V, with ~16-bit precision. I've seen evaluation boards from Analog Devices that offer 40 channels with the specifications, but they can only handle 1 mA load current. Does anyone have any suggestions for pre-made systems that could handle this sort of situation?

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closed as off-topic by Michael Karas, tcrosley, Matt Young, alexan_e, Daniel Grillo Feb 3 '14 at 18:50

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up vote 4 down vote accepted

DACs typically don't sink or source much current; typically to drive the output harder you use an op-amp which can drive to your requirements on the output of the DAC. If you need even more current than that, you can use a pass transistor or FET on the op-amp output and close the loop around it.

TI has a three part series on interfacing op-amps to DACs which probably goes into a lot more detail than you're after, but which I'm providing here for others interested in it.

Op-Amps for Everyone has an entire chapter (both safari online links) on interfacing DACs to loads which you might find enlightening, in particular "Current Boosters" in 18.7.1.

This psocdeveloper forum post goes into more detail about using a FET in the output path of a voltage-following op-amp which is connected to the output of a DAC in order to boost the current capability of the DAC. As I mentioned though, practically any op-amp can give you 10mA sink/source capability so you probably do not need to go this far.

A quick Digikey search shows op-amps like the MAX4495, AD8625 and HT1104 can supply 15mA per channel. You might want to take a look there and see where it leads you.

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I'm hoping to do this without generating a new PCB. digikey.com/product-search/… – nick_name Feb 3 '14 at 15:24
^^a DAC that can supply 1mA/channel with 40 channels. Is there any "buffer board" that can amplify the current for many channels that you've heard of? – nick_name Feb 3 '14 at 15:25
If you're trying to replace an existing DAC device, could you generate a piggy-back PCB that drops onto the existing one in place of the DAC chip but includes the buffers? I think you're on a long-shot finding a DAC with the capabilities you're after that will drop-in in place of whatever you're already using, pin-for-pin. – John U Feb 3 '14 at 15:40
@nick_name I don't know of anything off the shelf like that, no. – akohlsmith Feb 3 '14 at 22:08

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