## MOSFET transistor equations

Here we explain MOSFET transistor equations and we know MOSFET is a multiple junction semiconductor device, multiple parameters make enormous equations based on MOSFET.

So in this post, we include some of the important MOSFET transistor equations.

## N-MOSFET equations

### Cut-off region

• Drain current – iD= 0
• Gate to source voltage = VGS < VTN

### Linear region

• Drain current – Id= Kn (W/L). (VGS – VTN)VDS
• Gate to Source voltage = VGS > VTN
• Gate to drain voltage = VGD > VTN

### Saturation region

• Drain current – Id= ½ Kn (W/L). (VGS – VTN)2
• Gate to source voltage = VGS > VTN
• Gate to drain voltage = VGS < VTN

## Threshold voltage equation

VTN = VTO + ℽ(√2ϕf + VSB – √2ϕf)

## Transconductance equation

gm=2ID/ VGS – VTN

## Maximum operating frequency equation

fT= gm/ 2π(Cgs + Cgd)

## P-MOSFET equations

### Cutoff region

• Drain current – iD= 0
• Gate to source voltage = VGS > VTP

### Linear region

• Drain current – iD= Kp (W/L) . (VGS – VTP) VDS
• Gate to source voltage = VGS < VTN
• Gate to drain voltage = VGD < VTN

### Saturation region

• Drain current – iD= ½ Kp (W/L) . (VGS – VTP)2 . (1+λ . VDS)
• Gate to source voltage = VGS < VTP
• Gate to drain voltage = VGD > VTP

## Threshold voltage equation

VTP = VTO + ℽ (√2ϕf + |VSB| – √2ϕf)

## Transconductance of equation

gm=2ID/ VGS – VTP

## Maximum operating frequency

FT = gm/ 2π(Cgs + Cgd)