Answer to Question #152984 in Quantum Mechanics for Charudatta

Question

Define FET parameters obtain relation between them

Answer 1

Major FET parameter

• Gate Cut Off Voltage (VGS(off))

The relation between gate to source voltage and drain current is given below.

$I_D = I_{DSS}[1-\frac{V_{GS}}{V_{GS(off)}}]^2$

• Shorted Gate Drain Current ($I_{DSS}$ )
• Transconductance ($g_m$ )

$g_m = \frac{\delta ID}{\delta V_{GS}}$ at constant $V_{GS}$

• Dynamic Output Resistance ($r_d$ )

$g_m = \frac{\delta ID}{\delta V_{GS}}$ at constant $I_D$

• Amplification Factor (μ)

$\mu = \frac{\delta V_{DS}}{\delta V_{GS}}=\frac{\delta V_{DS}}{\delta I_D} \times \frac{\delta ID}{\delta V_{GS}}$

$\mu = r_d \times g_m$

Where,

$I_D =$ drain current

$V_{GS} =$ gate to source voltage