Question

5. (a) With the aid of a well-labelled disgram, describe in detail the operation of a p-channel MOSFET 15 marks) (b) Mention the modes of operation of a n-channel MOSFET with their corresponding equations for the drain current 16 marks (c) Give three (3) reasons why CMOS technology is preferred to NMOS technology in modern electronic devices? 13 marks) 6. (a) Why are some logic gates referred to as universal gates? Mention two universal cates and provide the truth table with three (3) inputs (A,B,C) for one of them. 16 marks (b) Show by a well-labelled diagram how any of the universal gate is used to accomplish the operation of an OR gate, 15 marks) (c) The output of a combinational logic circuit for a home security system gives an output of 1(HIGH) only when any one of the following patterns is present at its three inputs (A,B,C) f(A,B,C) (001,010,011, 100, 111) 1. Draw the truth table of the output function F(A,B,C). 14 marks]

Answer 1

cutoff Saturations regionale, Shado a Ivas for different VG we region points for operations Vgs-uto e get different region of . Similarly for Nl-mos we use p substrate to create Channel we should apply the voleage for gate x drain in order to operate Vds. I vas-Van - Saturation Vds <vas-Van -. Triode Atel . Triode Cutoff Saturation I Vox UT

Drain Current equation for fraction ( Jod- Len con e Cu Gs - Un) (e+-4 vas) t- Chamel length worlulation factor w a Width to leagth of mostET tale terminada Uncon - Capacitane of for Tho de regis Id lle con lo (Vas ") as-vas As var ? Jd 1 we prefer cmos instead almos because in order to get logic o and 1 'N mos cannot provide where as cmos can give both okl (mos has very low Static power consumpa lie power consumed when not in use is V -toon wy) noise immanity And it also has high CMOs Inverter Motos -Г-4 Here we get 'I' when ponos is I ON & Wmos & OFF o when emos is l OFF ANMOS is on No drop when mos is on we get o output but when off we get (vold- Idro) instead Udd. There is a dup

we use NAND & Nor gates as Universal gates, because we can implement any kind of gates logic through Nand, Nor NAND THith table, wore A B C . | X= ABC / - IX A+Btc ooo: 6.000 -- - oo -0- -ooooooo - ilo - - To get or using NAND we need 'B' Wand gates AED Konto

OR using Nor -2 gater Ate AR Gate I NANDI NOR] Trick Not to Easily remember XOR No. of gater X NOR I - required -dmth ins +(ABC) = Sm (1,2,3,4,7) S ACT AB TBC + ABC (ABC) = Ac+AB+Be+ ABC Truk tate LA, Bc f A tooo -0 010 Oil -0 004 co vote

I have provided a trick to easily know number of nand and nor required to get all gates.

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