Question

Questions s-11 refer to the multi-stage amplifier shown. + (β + 1)R h(1 + B.R) to make thern a little simpler. Clain expressions use the small approximation 5. What is the function of transistor Qs? CB gain stage (ii) CC buffer VEE (iii) CE gain stage (iv) active load for Qio (v) current source for Qio 6. What is the function of transistor Qio? Gii) current source for Qs (Ciii) CE gain stage (iv) active load for Qs (v) both current source and active load for Qs 7. What type of output stage does this amplifier use? (iii) AB (i) A (ii) B (iv) C 8. What is the main disadvantage of this type of output stage? G) it requires both n-type and p-type fabrication on the same chip (ii) it requires both positive and negative power supplies (iii) it has low gain s 1 (iv) it has low power efficiency (v) neither transistor conducts for small Vin, causing output distortion 9. What is the differential gain of the input stage? (i) ½gm2R12, where R12-ro2//rallrs(1 + Br sRi) (111) gm2RL2, where RL2 = roallroallrs(l + gmSR) (ii) gm2Ru2, where Rt., r altoallrs(1+ g sr%) (iv) grn2R12, where Ri': TaltoA 10. What is the gain of the 2nd stage? (i) Sm5k15, where Rs oos oll EmsRL5 I+gm5RL5 1+ gm5R1 (iv) gm5 R L5 m5KL , where RLs = roolit (1+g 1) g 5RLs, where RL,-Toollr s(1+gn5R1)Jr 6 1+gm5R What is Rin (Rid) of the amplifier? li) ( a)(+ gmo) ii) x2 (iv) co with no R

Answer 1

5. the function of the Q5 transistor is not a pnp active load insted it is CE gain stage. since the input at base terminal and output at collector terminal emitter is common to both input and output.

6. function of the Q10 is current source for Q5

7.since the output stage contains complementary pair of transistors therefore it is class B output stage.

8. the main disadvantage of class B output stage is cross over distortion

i.e.in the options neither transistor conducts for small Vin, causing output distortion.