Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
You can replace them, but the threshold voltage of a NMOS transistor increase if its source and bulk terminals are not at the same potenctial!! So, if you don't have enough voltage from VDD to GND, some NMOS transistors can not turn on!!
And Usually NMOS transisitors are closer to the ground and PMOS transisitors are closer to the VDD!!
PMOS is formed in Nwell, so it's bulk can be connected to source, while NMOS is formed in P type substrate. if you put NMOS close to Vdd, then the Vth will vary with the source voltage of the NMOS. So the output current will be not stable.
You could do it as suggested by using Depletion mode NMOS.
BUt using normal NMOS in a CMOS process, I donot think it can be done.
For example:
think of a NMOS current source for a PMOS differential pair.
Also think of a constant -gm circuit , for the lower NMOS diode what would be its VGS and hence the vdsat. And if this is used to bias some other circuitry, think how it would effect the output swing
I could not look at the brighter side
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
