Hi, I'm no expert in CMOS technologies, but I know that in typical CMOS circuits your P-channel devices are attached to Vdd and your N-channel devices are attached to Vss. For the case of passing a signal using the transistors for switching, if you try to pass Vdd with an N-Channel its value will be degraded, but passing Vss will be fine. The opposite holds true for P-Channel, ie passing Vss will be degraded but Vdd is fine. The reason for this is as follows: N-Channel is turned on with Vdd. If you are passing Vdd, ie you want Vdd on drain and source, then your output Vs will actually be Vdd-Vgs because of the material properties of the device. P-channel is turned on with Vss. Passing Vss, you'll have Vss at gate, drain and, presumably source, but the same holds. you need Vgs. so your output will be |Vgs|. Hope that helps. Wade ----- Original Message ----- From: "Andrew Hooper" To: Sent: Sunday, October 14, 2001 1:36 PM Subject: [EE]: Mosfet N-Chanel switching I'm trying to build an H-Bridge for inductive loads using n-channel fets. The fet that has its source connected to ground and the load connected between the 18V+ rail and drain I get full power. (around 18 volts appears between negative and drain) But the fet that has its drain connected to the vcc and the load connected between the negative rail and source I'm getting a considerable amount less power. (only about 15.5 volts appears between negative and the load) Am I barking up the wrong tree or should this work? The reason for using n-channel is that they are easier to get and less expensive. Thanks in advance for the assistance. Andrew Hooper -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads