Good day to all. I got burned with a bad decision I made on one of my projects. This is a fairly major revision of an existing board that used to be based on one of the Microchip 14 pin PICs (16f630). I needed at least two more pins and simply went to the next larger parts in that family (16f630 -> 16f631). Turns out there are a few significant differences between those 2 parts. One of those caused minor problems, one is now going to cause me major grief. 1) The 16f631 doesn't have the analog mux that allows Comparitor 1 to be used on both RA0 or RA1 while also using the internal Vref. OK - so now I have to use the 16f77 and read the analog level on pin RA0 with the a/d instead. No problem. 2) Major "gotcha" for me: all 8 pins in Port C have changed from TTL input thresholds to ST thresholds. My bad - I didn't check the datasheet closely enough. I rely on the low input threshold of the TTL inputs to allow me to sample voltages from an un-regulated supply - this allows me to tolerate supply variations of plus 40% or minus 60% with no problems. Not so with ST inputs. A complicating factor is that the lines that feed those inputs on Port C can also be jumpered (via diodes) to a bus that drives the input of a digital transistor (DTC143ES). For those that don't know, a "digital transistor" is a transistor with built-in base bias resistors - a series resistor on the base input plus a shunt resistor between B-E. I'm using those because of space limitations on the board. The internal resistors on the digital transistors I'm using are nominal 4k7 each. Because I now have a much tighter voltage tolerance on the Port C inputs, I can't tolerate the loading of those digital transistors. Simply too much variation on the logic HI level. I have a couple of options: I could change the voltage divider resistors that feed each of the Port C inputs and add zener diode clamps to ensure the voltage never rises above Vdd. I would pick the resistors such that a logic HI was solidly above the upper threshold even if a PortC input was also jumpered to the buss driving the digital transistor. Or - I could use a transistor that doesn't load down the buss. That is: use a small TO-92 MOSFET in place of the digital transistors. My favorite small MOSFET is the 2n7000. Problem is: the Vgs threshold can be a low as 0.8V. That's far too low for my application - I need something that is absolutely OFF so long as Vgs is less than 1.3V or so. It also has to be solidly ON at Vgs exceeding 3.5V. An added bonus would be having a pinout of S-D-G (or G-D-S). The max voltage on the drain is 35V, max current is 30 mA. My question is: does anyone have a favorite N-channel leaded MOSFET in a TO-92 package or similar with those specs. That is: N-channel Vds 35V minimum Id 30 mA minimum Vgs OFF: >= 1.3V Vgs ON: <= 3.5V Many thanks! dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist