LT1970 Current source mode (DC2591A)

Question

Hi everyone, 
 According to the demo manual DC2591A , the EasySMU board is described as a 'programmable-voltage/programmable-current' source (see the attached image from the first page of the datasheet). 
 I assume this functionality is provided by the LT1970 Power Op Amp at the core of the board. However, I'm a bit unclear on how it's being used as a current source. From what I can see, the EasySMU code doesn&rsquo;t appear to directly set an output current (by set, I mean force like an SMU would); it seems to only set a current limit (using the ' fltSetCommitCurrentSource() ' and ' CommitCurrentSourceSetting() ' functions). 
 I've run some simulations with LTSpice using the provided model of the Op Amp, but I haven't been able to achieve a constant current through any load. 
 Could someone clarify how the current source functionality is implemented ? 
 Thanks a lot !

GLADION · Answer

Hi PiR , 
 Good day. The two channels of the LTC2655 configures the VCSRC and VCSNK pins. These pins configure the output source and sink current limits. 
 
 There also some configurations from LT1970A datasheet where the part is configured as a current source. Thank you. 
 
 Regards, Gilbeys

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LT1970 Current source mode (DC2591A)

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