0
\$\begingroup\$

If they do exist, what is advantage of using them? How often are they used in comparison with mosfets that have integrated diode?

\$\endgroup\$
  • 2
    \$\begingroup\$ Which diode? The intrinsic body diode, or the extra ESD protection? \$\endgroup\$ – CL. Jan 11 at 20:15
  • 1
    \$\begingroup\$ What exactly do you mean by "protection diode"? Are you referring to a gate-source zener or to the parasitic body diode? \$\endgroup\$ – Spehro Pefhany Jan 11 at 20:15
  • \$\begingroup\$ I mean diode between drain and source. \$\endgroup\$ – Etwus Jan 11 at 20:17
  • \$\begingroup\$ That diode is intrinsic to the mosfet structure and cannot be removed. It's not a part that's intentionally added. \$\endgroup\$ – Hearth Jan 11 at 20:21
  • 3
    \$\begingroup\$ It's worth mentioning also that the diode isn't technically between drain and source; there are two diodes, one between drain and body and one between source and body. In most cases, but not all, body and source are internally connected together, so the source-body diode is shorted out and the drain-body diode becomes effectively a drain-source diode. \$\endgroup\$ – Hearth Jan 11 at 20:34
3
\$\begingroup\$

It's possible to manufacture 4-lead MOSFETs with the body connection (aka "back gate") brought out, but I think they are pretty rare.

You'll see parts with the body not tied to source used in chips, for example to make a good transmission gate.

enter image description here

In the above, when the body is tied to Vcc the diode junction does not become forward biased until the voltage exceeds Vcc, allowing the TG to pass signals over the whole GND to Vcc range.

\$\endgroup\$
  • \$\begingroup\$ Can you clarify here? The NMOS body voltage must not exceed ground+Vd and the PMOS body must be greater than Vcc-Vd, I think. Assuming that at least one PMOS source is connected to Vcc and one NMOS source is connected to ground. \$\endgroup\$ – Elliot Alderson Jan 11 at 21:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.