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MOSFET in Linear Region

A depletion t...

Question

A depletion type N-channel MOSFET is biased in its linear region for use as a voltage controlled resistor. Assume threshold voltage $V_{T H} = - 0.5 V$ , $V_{G S} = 2.0 V$ , $V_{D S} = 5 V, W / L = 100, C_{o x} = 10^{- 8} F / c m^{2}$ amd $μ_{n} = 800 c m^{2} / V - s$ . The value of the resistance of the voltage controlled resistor (in $Ω$ ) is ____
500

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Solution

The correct option is A 500
Voltage controlled resistance $r_{D S}$ is given by
$r_{D S} = \frac{1}{(μ_{n} C_{o x}) (\frac{W}{L}) (V_{G S} - V_{t})}$
$r_{D S} = \frac{1}{800 \times 10^{- 8} \times (2 + 0.5) 100}$
$r_{D S} = 500 Ω$

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Similar questions

A depletion type N-channel MOSFET is biased in linear region for use as a votlage controlled resistor. At V_{G S} = 2 V, the drain to source resistance (r_{d s}) found to be 500 Ω, if V_{G S} is increased to 3V, then the value of rds is______Ω (Assume, Threshold voltage, V_{T h} = - 0.5 V, the value of V_{D S} to be very small)

W

L

μ_{n}

C_{o x}

V_{G S} = 0.7 V

V_{D S} = 0.1 V, (μ_{n} C_{o x}) = 100 μ A / V_{2}

V_{T h} = 0.3 V

(W / L) = 50,

g_{m} (i n m A / V)

V_{G S} = V_{D S}

(V_{T})

1 V

(I_{D})

1 m A

V_{G S} = 2 V

V_{G S} = 3 V, I_{D}

A n i d e a l n - c h a n n e l M O S F E T h a s t h e f o l l o w i n g p a r a m e t e r s, t h r e s h o l d v o l t a g e V_{T} = 0.65 V a n d o x i d e t h i c k n e s s i s 0.4 n m . I t i s f o u n d t h a t t h e M O S F E T o p e r a t i n g i n s a t u r a t i o n r e g i o n w i t h V_{D S} = 6 V . T h e n t h e p o w e r d i s s i p a t i o n i n t h e M O S F E T w i t h V_{G S} = 4 V i s μ_{n} C_{a x} \frac{W}{L} = 1.5 \times 10^{- 3} A / V^{2},

1 μ m

10 μ m

N_{A} = 5 \times 10^{16} c m^{- 3}

μ_{n} = 800 c m^{2} / V - s

C_{o x} = 3.45 \times 10^{- 7} F / c m^{2}

V_{T} = 0.7 V

(I_{D s a t})

5 V

ϵ_{0} = 8.854 \times 10^{- 14} F / c m, ϵ_{S i} = 11.9

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