I have posted a hand drawn schematic at http://oh-god.com:5080/dir/Electronic-load/ The application is a battery tester. I want to load a 1.5 to 5V battery with a load current of zero to 40A. To the right you see I plan to drive the op amp with a 16 bit DAC. R3 shuts off the load if the DAC is disconnected. I put in R1 and R2 as insurance. I am not sure I need them at all. The EL can be very slow. A response time of 1 second is okay. Rsense is .01 ohms. Thus I figure that Vsense will vary from 0.0 to 0.4V. The FET will be using a heatsink ( and maybe a fan ) and will be rated at about 80A and 300W. I have calculated the power dissipation of the FET to be a max of 40A times 5V which is 200W. ( Some of that heat will appear across Rsense ) DAC = DAC8574 FET = FQP90N10V2 OP AMP = ??? Will this idea work or have I missed the banana boat. What would be a good op amp to maintain precision ? The op amp need not be fast. Low power is obviously not a factor. MA WFT Electronics Denver, CO 720 222 1309 " dent the UNIVERSE " All ideas, text, drawings and audio , that are originated by WFT Electronics ( and it's principals ), that are included with this signature text are to be deemed to be released to the public domain as of the date of this communication . WFT Electronics Denver, CO 720 222 1309 " dent the UNIVERSE " All ideas, text, drawings and audio , that are originated by WFT Electronics ( and it's principals ), that are included with this signature text are to be deemed to be released to the public domain as of the date of this communication . WFT Electronics Denver, CO 720 222 1309 " dent the UNIVERSE " All ideas, text, drawings and audio , that are originated by WFT Electronics ( and it's principals ), that are included with this signature text are to be deemed to be released to the public domain as of the date of this communication . -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist