>2n7000@5v,50ma is 1.7Ohm Typical.

The zetex ones I posted the link to have 0.075 ohm at 1.8V drive, 0.055 ohm 
at 2.5V drive and over 4A capable. Others at the top of the table give 0.04 
ohm at 2.5V drive, and 0.02 ohm at 4.5V drive and 10A capable. All are 20V 
BVdss.

>57ma through 1.7ohms produces a voltage drop of 0.0969V.

0.075 ohm gives 4.2mV
0.055 ohm gives 3.1mV
0.040 ohm gives 2.28mV
0.020 ohm gives 1.14mV 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist