Depends - is it a junction FET or a MOSFET? If a junction FET then the gate will form a diode rectifying whatever signa= l appears at the drain from the transformer, but the channel in the FET wil= l probably be conducting as they behave like valves and need a reverse bias= on the gate to turn the channel off. If a MOSFET then there is usually a d= rain-source diode which in normal operation is reverse biased, but if the o= utput from the transformer is of large enough amplitude it will become forw= ard biased and charge the 100uF cap. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of David = Van Horn Sent: 23 January 2019 15:31 To: Microcontroller discussion list - Public. Subject: [EE] Here's an odd question: Take a common P Fet, in this case an AO3435 from = Alpha and Omega. Ground the drain. (Actually connected to a small winding on a transformer, = but <<1 ohm DC path to ground) Connect the source to ground through 47k Con= nect the gate to the source through 100k. Connect a 100uF capacitor to the source and ground. Is the FET on, or off in this condition? My expectation is that the FET is off, and only parasitic capacitances conn= ect the 100uF on the source lead to the drain lead. -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=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 .