Should I pick up npoly or ppoly as a resistor loads?

[casual]

For a nmos CML logic eg: typical CML latch, should I pick up npoly or ppoly as a resistor loads? The voltage swing is from Vdd to Vdd-swing, Does it have any difference to use npoly or ppoly if Rsheet is about the same

 

[fredflinstone]

npoly vs ppoly resistor

i think you can use either of the two in your design.

 

[erikl]

Re: npoly vs ppoly resistor

... should I pick up npoly or ppoly as a resistor loads? Does it have any difference to use npoly or ppoly if Rsheet is about the same

In most processes, npoly and ppoly have different TCs, s. your PDK docu.
If temperature dependency is an issue, you could decide upon your preference.

 

[casual]

Re: npoly vs ppoly resistor

It must have difference in term of reverse biased capacitance. I think npoly is better if the swing is near to vdd since the reverse biased voltage is larger, thus smaller capacitance. Does anyone agree??

 

[erikl]

Re: npoly vs ppoly resistor

It must have difference in term of reverse biased capacitance. I think npoly is better if the swing is near to vdd since the reverse biased voltage is larger, thus smaller capacitance. Does anyone agree??

I don't, sorry! Resistor poly sits on TOX, so there's no junction and hence no reverse bias capacitance, just the fixed TOX cap.

Your argument is valid for diff resistors, however.

 

[casual]

npoly vs ppoly resistor

thank you