A multi-stage amplifier is shown below. Don\'t worry about any numbers for this

Question

A multi-stage amplifier is shown below. Don't worry about any numbers for this problem. a) What is the purpose of transistor Q_5? (i) CE gain stage (ii) CC buffer (iii) CB gain stage (iv) active load for Q_10. (v) current source for Q_10 b) What is the purpose of transistor Q_10? (i) current source for Q_5 (ii) active load for Q_5 (iii) CE gain stage (iv) both current source and active load for Q_5 (v) CC buffer c) What type of output stage does this amplifier use? (i) A (ii) B (iii) AB (iv) C (v) it doesn't have an output stage d) What is the main disadvantage of this type of output stage? (i) it requires both n-type and p-type fabrication on the same chip (ii) it requires both positive and negative power supplies (iii) neither transistor conducts for small v_in, causing output distortion (iv) it has low power efficiency (v) it has low gain lessthanorequalto 1 e) What is the differential-mode input resistance (R_id) of this amplifier? (i) r_x1||r_x2 (ii) r_k1 + (beta + 1)(2r_o9) (iii) r_x1 + r_x2 (iv) r_x2 (v) 2(e_x1 + r_x2) f) What are two main advantages of using active loads compared to resistive loads? (i) higher gain and less area on an IC (ii) higher gain and higher R_in (iii) higher R_in and R_out (iv) less area on an IC and better frequency response

Explanation / Answer

A) option 4.

actually gain obtained from differential amplifier must be amplified. Generally on IC large valued resistances are not possible to use. To limit that use transistor as a high resistance a gain has to be increased. So active load is the answer. This active load has high resistance and high gain

B)option c

To increase the gain. It is ce amplifier by basic of observation.

C)its using class c power amplifier. Option d.

D) option c. At last stage we are class c specially because of high power efficiency. Yes distortion is higher in this configuration.

E)by drawing the rpi equivalent model we get option c

F)doesn't relative input resistance. Its increases output resistance and reduce size on the transistor. So option A

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