I'm diving back in to discrete component circuit design again after a few years, and I'm blanking out, is there any functional difference between an n-channel transistor and an NPN, same for p-channel PNP transistors?
Thanks.
NPN / N-channel
Feb 17, 2007
2 Replies
** Worried Groper alert !
** The word "channel" implies the device is a FET ( Field Effect Transistor).
Lots of interesting differences between a FET and a BJT (ie Bi-polar Junction Transistor)
Do a Google search......
....... Phil
*If* the device is a MOSFET (and not a JFET), you can *almost* treat them the same as BJTs, at least for switching.
Similarities:
drain = collector source = emitter gate = base
driving base relative to source enables current from drain to source.
Differences:
BJTs are current controlled current devices. MOSFETS are voltage controlled resistor devices. The response curve is different.
So, where driving a BJT with a base current (Ibe) enables a much larger collector current (Ice), driving a MOSFET with a gate voltage (Vgs) reduces the drain-source resistance (Rds). Also, the gate has a small capacitance, so you not only have to drive it ON, but you have to drive it OFF too. The capacitance also affects the frequency response, so model it if you're doing high frequency work.
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