Look up the datasheet for the NTD20P06L (or any P-channel mosfet) and see if you reach the same conclusion.
John
I'm missing your point.Some confusion may arise from the similarity of names. What was originally meant by "mosfet" was a device much like the ubiquitous MPF102 - a small, very low power amplifier with a large input impedance.
The power variations actually use thousands of paralleled cells like those individual mosfets, and might be more accurately referred to as "hexfets" - http://en.wikipedia.org/wiki/Power_MOSFET
The MPF102 is symmetric as indicated. Voltage on the gate will promote conduction between the other terminals, and polarity is not significant. An IRF510 (for instance) is not like that, as the drain must be positive with respect to the source.A MOSFET is a symmetric device, therefore the terminal which has the higher voltage would be the drain and the lower would be the source?
MPF102 is a JFET. All MOSFETs have a substrate (body) which must be connected to some voltage. Most are 3 pin devices, with the body tied to the source. Four pin devices such as SD210 bring out the body on a separate pin.From the original post - The MPF102 is symmetric as indicated. Voltage on the gate will promote conduction between the other terminals, and polarity is not significant. An IRF510 (for instance) is not like that, as the drain must be positive with respect to the source.
Well, I used to know that....MPF102 is a JFET
Of course, when off, there is also reverse conduction through the intrinsic diode. A circuit that used the "on" reverse conduction property to advantage would be interesting. What would be required to keep the gate turned on during reverse conduction? Perhaps there is a compilation of odd circuits for mosfets that someone knows about.Source:http://www.microsemi.com/micnotes/APT0403.pdf
If the gate-source voltage is at or above
what is called the threshold voltage, enough electrons
accumulate under the gate to cause an inversion n-type
layer; forming a conductive channel across the body
region (the MOSFET is enhanced). Electrons can flow
in either direction through the channel.
I have read that once on, a mosfet conducts in either direction. For example:
Of course, when off, there is also reverse conduction through the intrinsic diode. A circuit that used the "on" reverse conduction property to advantage would be interesting. What would be required to keep the gate turned on during reverse conduction? Perhaps there is a compilation of odd circuits for mosfets that someone knows about.
John
So it would be yes for an nmos since with how drain and source are defined, electrons will flow from the source to the drain only when an E field is established directing from the D to the S in terms of a higher voltage at the drain.A MOSFET is a symmetric device, therefore the terminal which has the higher voltage would be the drain and the lower would be the source?
wait a minute, I guess I was refering to an nmos you used as a switch in cmos technology, with p substrate and n wells.I can't tell if both of the above posts refer to my comment about conduction. I used conventional current and for simplicity refer only to the N-channel mosfet. When the mosfet is turned on, current normally flows from Drain to Source. When it is off, the intrinsic diode will conduct from Source to Drain. However, it is stated in many places, including the Microsemi link, that when On, the mosfet conducts equally in both directions (Drain-to-Source = "forward" and Source-to-Drain = "reverse"). That is consistent as well with your quote from Razavi.
I have never studied that reverse conduction and was wondering if it had some practical usefulness.
John