What is the purpose of having pass gate on the power line instead of ordinary single pmos device?

Thread Starter

Vahram Hambardzumyan

Joined Jul 29, 2017
I want to minimize one of my schematic and looking possibilities to get rid of several single to differential converters which are actually intended to switch on/off pass gates. Can I just use pmos transistors instead of pass gates? On the power line(vdd), I think just single pmos should work, since there is no logic 0 and 1 signals there.

Thread Starter

Vahram Hambardzumyan

Joined Jul 29, 2017
Pass gates or transmission gates are devices widely used in CMOS technology to switch on/off signal lines. In my application there is a need to switch on/off power lines , not signal lines, and for that purpose I'm looking to replace those devices with pmos transistors.



Joined Mar 14, 2008
How much voltage do you want to switch?
Transmission gates typically only switch less than 15V or so.


Joined Sep 17, 2013
..... and the voltage the gate switches must lie between the gate's supply rail voltages.


Joined Aug 1, 2013
Normally, a p-channel MOSFET is an excellent power switch. For output voltages above 20 V the gate drive circuit has to change, but not by much. This approach works up to the kilovolt range.

But for very low output voltages a p-channel device makes the circuit more complex, because now the gate has to be negative with respect to the output voltage. For example, if you want a nice solid gate drive withal of 10 V, then Vgs = -10 V, or -8.2 V with respect to the +1.8 V output. Better to use an n-channel FET, where thegate drive voltage can come from some other, higher system voltage. What other power supply voltages are available for the drive circuit?