Value of Vout in PMOS Inverter?

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SUMMARY

The discussion focuses on deriving the output voltage (Vout) equation for a PMOS inverter. The participants clarify that while the equation for an NMOS inverter is Vdd - id*rd, the PMOS inverter's output can be expressed as Vout = id * Rd when considering the resistor's position. The resistor's placement at the bottom of the PMOS inverter alters the output behavior, leading to a simplified understanding that Vout can equal Vcc when the output is logic HIGH.

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  • Understanding of PMOS and NMOS transistor operation
  • Familiarity with inverter circuit design
  • Knowledge of Ohm's Law and basic circuit analysis
  • Experience with voltage output calculations in digital circuits
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jean28
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Hey guys. I am simply trying to derive the equation for Vout in a PMOS inverter (attached). I know that in an NMOS inverter (which has the resistor in top of the transistor instead of the bottom) the equation for Vout is:

Vdd - id*rd.

But how does the resistor being in the bottom change this behavior? Is it now Vcc - ground? (which would equal Vcc).

Thanks.
 

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It could also be Vout = id * Rd.
 
jean28 said:
It could also be Vout = id * Rd.
If by Rd you mean that external resistor, then that looks right for output logic HIGH.
 

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