Question

D. Since a frequency response as seen in C. is clearly unacceptable, the capacitor Cl is used to decrease the feedback signal at higher frequencies. Components are chosen as follows: R1-320k2, R2-10k2, C1-4.7nF. The transfer function of the feedback network is therefore 10, 000 Ro GRVoUT() urs) RRC1+RR 15.5330, 000 Determine the combined transfer function IsPx(s)/V(s) when the frequency compensation capacitor CI is installed and determine the poles and zeros (if any) of the new transfer function. [10 points] Problem1 Hi-fi audio amplifiers are usually built as discrete difference amplifiers with a rel- atively large gain (near 55dB or more) and with built-in feedback that reduces the closed-loop gain to a much smaller value in the range of 30- 35dB. Since loudspeakers predominantly act like a resistor (nominal impedance: 4Ω) with an inductor in series, the feedback network can also be used to improve the frequency response in the audio range up to 20 kHz. In this problem, we are primarily con- cerned with gain and frequency response of the amplifier. Amp Vour(s) R1 : R C1 R2 FeedbackL Network Speaker Impedance GFB(s) Speaker Impedance Discrete operational amplifier Vour(s)1 V(s) Vre(s) Figure 1: Simplified schematic (A) and block diagram representation (B) of a hi-fi ampli- fier output stage with feedback network and loudspeaker impedance. The magnetic force that drives the membrane is proportional to the coil current Isp, and the coil current is therefore the output variable that we are interested in.

Answer 1

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