On Wed, Feb 6, 2013 at 2:18 PM, veegee wrote: > > Yup, the choice and number of transistors on the schematic is simply a > placeholder. Any power transistor (both MOSFET and BJT) simulated well > so far. > Yes, I figured you just grabbed one that was convenient to the simulator. (I think a proper simulator should show a little cloud of smoke over a component when it exceeds max junction temperature, but I've never seen one do this...) > I already have 30 or so large TO-220 type power MOSFETs for the job. > Don't have the part number with me at the moment, but I chose them > specifically for low Rds_on, high current rating, and high power > dissipation. Remember, a low Rds_on is meaningless in a linear application like this one= .. > For some reason, BJTs always make me feel better. I might just go ahead > and buy a bunch of TIP122 or TIP142 power Darlingtons. I'm guessing BJTs > will give me far better transient response anyway, given the large gate > charge of those low Rds_on MOSFETs, but I have yet to simulate that. You are measuring current upstream from the output transistors, so if you go BJT you will have error introduced by the base current, which will be added to the output current. The resultant error may be acceptable with Darlington outputs. --=20 Regards, Mark markrages@gmail --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .