# MOSFET question.

Discussion in 'Homework Help' started by Ledwardz, Jan 5, 2013.

1. ### Ledwardz Thread Starter Member

Oct 31, 2010
37
2
Hi people.

I am given the table below with the following questions.

It asks me to find which of the following are NMOS and which are PMOS. my initial thinking was to use gm = WμCox (Vgs-Vt) / L

assuming that N mos were quicker because electron mobility was higher compared to that of holes. I used the data sheet to find that Ue = 1500 and Uh is = 450

I made a few assumptions the first being that Vt was 0.25Vds

can i ask when it says operation voltage = 2.5V, does that mean that Vgs = 2.5 or Vds = 2.5??? and if so what is the voltage on the top of the table??

I assume the transconductance gm in the table is gm / W because of its units however i have no idea what the S in the units are for and is mm milimetres? i assume not... i also know that gm is measured in mho.

anyways i put the numbers in and err well i got mobility = 0.0034 m^2/ Vs

which i think should equal 33 cm^2 / Vs

this doesnt = 450 or 1500?????

have i done something stupid??? any ideas????

Lee.

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2. ### Ledwardz Thread Starter Member

Oct 31, 2010
37
2
To add to this how can i tell if it is acting in the linear or saturated region? I know that it is saturated as VD approaches (Vgs- Vt) but can't really answer that until i know what the top line of the table means.

3. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
The modern unit for conductance is Siemens, abbreviated 'S'.

Oct 31, 2010
37
2

Okay thanks.