James said:
Can anyone recommend a small (<=sot-23), low cost FET to switch
a 3V 2mA load? I would like it to be on the high side of the
load and have a micro port pin drive the gate.
A standard answer would be a p-channel MOSFET, or perhaps a PNP
transistor. But the MOSFET would have to be a low-threshold-
voltage type, and the PNP would require a base resistor. So we
have excuses to keep looking.
I think a good candidate would be a 1-gate logic buffer, a
modern version of the old 74HC125 drivers. Consider 1G125
gates in the LVC family. These have Rout less than 30 ohms
at Vcc = 3V, so a 2mA load would drop less than 60mV.
TI's 74LVC1G125DBV uses a sot-23-5 package, with 0.95mm lead
spacing. Philips (NXP) part of the same size, 74LVC1G125GW,
says it's in a sot-753 SC-74A package. TI's 74LVC1G125DCK
uses a miniature sot-70 package, with 0.65mm lead spacing.
NXP's 74LVC1G125G says it's in a sot-353 (TSSOP5) package.
Sigh, whatever, no doubt both small 0.95mm parts will solder
onto those pads, and ditto for the miniature 0.65mmm parts.
The 74LVC1G125DBV and DCK are 39 cents at DigiKey qty 1.
The NXP parts are 30 cents, six cents in a full reel.