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Design >> Analog Design >> PMOS current source I-V characteristics
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Message started by Harian on May 2^nd, 2017, 1:39pm

Title: PMOS current source I-V characteristics
Post by Harian on May 2^nd, 2017, 1:39pm

Hi Everybody,
i have a basic Pmos I-v Characteristics question. A PMos in cadence is connected as following(pls, see the below picture)
While simulating it, i got pmos diode like curve not a normal pmos I-V curve as following https://en.wikipedia.org/wiki/MOSFET#/media/File:IvsV_mosfet.svg
can some one explaint he difference. I am simulation with cadence virtuoso. I would appreciate any help.. thanks

Title: Re: PMOS current source I-V characteristics
Post by Harian on May 2^nd, 2017, 1:41pm

Getting this curve whilw simulation,, But i think it is the typical i-v curve of pmos diode conencted,,isnot it?

Title: Re: PMOS current source I-V characteristics
Post by ULPAnalog on May 2^nd, 2017, 1:48pm

What is the gate source voltage?

Title: Re: PMOS current source I-V characteristics
Post by Harian on May 2^nd, 2017, 1:53pm

i have set to 0.9 volts i.e. Vgs=-2.3 v,, i have slo done parametric simulation sweeping the Vds from -3.3 to 0 and Vgs from -3.3 to 0 also.. the result is always the same curve.. then i have simulated A nmos with the polarity reversed,, it was the same result.. I am thinking ,, it might be simulation equation used,,thx for reply

Title: Re: PMOS current source I-V characteristics
Post by Nyquist on Oct 15^th, 2018, 11:23am

Hi Harian,

you have connected gate to a constant voltage and swept the Source voltage. In effect, you are actually sweeping VSG and plotting the Source current. The plot looks correct.

If you need to plot the ID-VDS Characteristics, then you need to connect a voltage source between Source and Gate (VSG). Now you can sweep VSD for different values of VSG to get the plot you want.

Nyquist