# The output resistance of FET when operating in pinch off at a current 10 mA and λ = 0.05 V-1 is given as

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The output resistance of FET when operating in pinch off at a current 10 mA and λ = 0.05 V-1 is given as
1. 450 Ω
2. 2 kΩ
3. 200 Ω
4. 2 Ω

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Correct Answer - Option 2 : 2 kΩ

Concept:

The output Resistance of FET is defined as

${r_o} = \frac{1}{{\lambda {I_D}}}$

Where λ = channel length modulator parameter

ID = drain current

Calculation:

Given

λ = 0.05 V-1

ID = 10 mA Important Point:

${r_o} = \frac{1}{{\lambda {I_D}}} = \frac{1}{{0.05 \times 10 \times {{10}^{ - 3}}}} = 2K{\rm{\Omega }}$

NOTE:

If MOSFET does not have a channel length modulator then ⇒ λ = 0

${r_{ds}} = \frac{1}{{\lambda {I_{DS}}}} = \infty$ (of P resistance)