Determine Drain current and region of NMOS transistor in the

Determine Drain current and region of NMOS transistor in the next circuit with a with: KP = 40 mu A/nu^2, nu_TO = 1.5 nu, L = 12.5 mu m and W = 250 mu m.

Solution

look nmos transister are two types

1. static

2.dynamics.

here the nmos transister are used for high speed switching.

Here we have

K_p = 40 µA/v²

_Vt0 =1.5 v

L=12.5 µm

W=250 µm

From the squar low modal of an n channel ,

Drain Current ,I_D is given by.

I_D=0, Cut off region,

I_D=K(V_GS-V_t)², saturation region

Here we assume that the nmos is in saturation region .

so for that

I_D=K(V_GS-V_t)² -----------(1)

from the gate- source loop by applaying KVL:

0.0-V_GS-5I_D=-10.0

SO, I_D= 2-0.2V_GS ---------------(2)

From the drain source loop by applaying KVL:

10-5I_D-V_DS-5I_D=-10.0

BY rewritting the equation,

V_DS=20.0-10I_D    --------------------(3)

BY equatting the equation (1) and (2),

K(V_GS-Vt)² = 2-0.2V_GS

By solving the above equation can get,

40V_GS²-119.8V_GS+88=0

WHERE, K=40,V_t=1.5

The above equation is in quadratic equation so we get two solution for that,

V_GS=1.7 V or V_GS=1.3 V

But for saturation region

V_GS>V_t

So,

V_GS=1.7 V is the right answer.

For V_GS=1.7 V

I_D=2-0.2V_GS   from equation (2)

So.

I_D=1.66 mA

So drain current, I_D= 1.66 mA for saturation region