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high voltage current sink&source DAC

Question asked by Christian_B on Dec 4, 2015
Latest reply on Dec 15, 2015 by Christian_B

Hi,

 

Sorry if this question seems (or actually is) a bit redudant but although i found several topics about current DAC/current buffers my requirements seems to be slightly different: I am looking for a system which is abled to translate a digital signal into currents up to +- 6mA against a resistive load of 1-5kOhm (so U_swing= R*I = 5kOhm * 6mA = 30V).

Currently we are using a combination of a mid voltage OPAMP (OPA192), a current sense (AD8418) and a voltage out DAC (AD7303) to build a current sink/source system but this requires 3 parts with a comparable hugh footprint and I want to cut down the space requirements.

So I was thinking of an bidirectional current DAC with a supply swing of >30V. I already found the AD5750 (25mm²) which would do the job if combined with a AD5621 (4-6mm²) but i wonder if there is an even smaller/better solution. Maybe there is a combination of a current DAC and current buffer? Or something bold as http://i.stack.imgur.com/jGoa3.gif with a bit more decent current control (because the PNP/NPNs i found have rather high gain deviation).

 

Background story: we are working on a bi directional neural interface there physiological electrical stimuli are provided via electrodes which have impedances of 1-5kOhm. As one wants to control the applied charge per pulse the current (sub mA up to several mA) and the pulse length (few ms) is set. Pulse trains with a frequency of around 50Hz are applied. As one wants charge balancing biphasic pulses are used (or monophasic pulses + block capacitors). Most critical is the space requirement.

 

Best regards,

Christian B.

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