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C192023 Pages:2

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An abrupt Si p-n junction has N, = 100” on one side and Ng =5x 10 ला on
the other. If the junction has a circular cross section with a diameter of 10um,

Calculate Vo, 5.० | ©+, and €o for this junction at equilibrium (300 K).

PART C
Answer any two full questions, each carries20 marks.
Derive the expression for minority carrier distribution and terminal currents in a
BJT. State the assumptions used.
Explain the basic performance parameters a, B & y.

Assume that a p-n-p transistor is doped such that the emitter doping is 10 times
that in the base, the minority carrier mobility in the emitter is one-half that in the
base, and the base width is one-tenth the minority carrier diffusion length. The
carrier lifetimes are equal. Calculate ൨ and 8 for this transistor.

Derive the expression for drain current at linear region and saturation for a
MOSFET.

An Al-gate p-channel MOS transistor is made on an n-type Si substrate with Na =
55107 ' cm 3. The 510) thickness is 100 A in the gate region, and the effective
interface charge Q; is 5 x 1010 q Clem’. Find Wm. Ves , and ۷ if the gate to
substrate work function difference Dms = -0.15V

Draw and explain the transfer characteristics of an n-channel MOSFET.

Explain the principle of operation of MOS capacitor with suitable energy band
diagram.
Explain base width modulation. Explain its effect on terminal currents.

Draw and label the minority carrier distribution curve of a BJT in active mode.

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