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

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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
 

Re: npoly vs ppoly resistor

casual said:
... 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
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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.
 

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??
 

Re: npoly vs ppoly resistor

casual said:
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??
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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.
 
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    casual

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npoly vs ppoly resistor

thank you
 

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