An engineer is trying to design a 60-dB audio amplifi er (that is, an amplifi er with A0 5 1000 V/V and fB $ 20 kHz) using an op amp with ft 5 1 MHz. Realizing that just one op amp won’t do it because...

An engineer is trying to design a 60-dB audio amplifi er (that is, an amplifi er with A0 5 1000 V/V and fB $ 20 kHz) using an op amp with ft 5 1 MHz. Realizing that just one op amp won’t do it because it would give fB 5 ft yA0 5 106 y103 5 1 kHz ! 20 kHz, the engineer tries cascading two stages with lower individual gains A10 and A20 but wider individual bandwidths fB1 and fB2. (a) If the engineer decides to impose A10 5 A20 5 √ _____ 1000 V/V, what are the bandwidths fB1 and fB2? (b) What is the overall 23-dB frequency of the cascade combination of the two stages? Hint: by defi nition, f23 dB is such that uA(jf23 dB)u5 A 0 y√ __ 2 , where A(jf) 5 A1(jf) 3 A2(jf). (c) What if the engineer had cascaded two stages of unequal gains but still such that A01 3 A02 5 1000 V/V, say, A105 20 V/V and A205 50 V/V? Would the overall 23-dB frequency still meet the specifi cations? Explain!