A student is experimenting with a certain amplifi er that has f23 dB 5 995 kHz, and wishes to fi nd experimentally the contribution from the stray capacitance Cxy and equivalent resistance Rxy between...

A student is experimenting with a certain amplifi er that has f23 dB 5 995 kHz, and wishes to fi nd experimentally the contribution from the stray capacitance Cxy and equivalent resistance Rxy between a specifi c pair of externally accessible nodes X and Y. Writing f23 dB 5 1y[2(RxyCxy 1 rest)], where rest is the sum of the time constants due to the rest of the stray capacitances, the student decides to measure f23 dB under different loading conditions to indirectly fi nd Rxy and Cxy. (a) If connecting an external capacitance Cext 5 10 pF between nodes X and Y lowers the bandwidth to f23 dB 5 612 kHz, what is the value of Rx? (b) If the student connects in parallel with Cext also a resistance Rext 5 Rx (to avoid perturbing the dc operating conditions of the circuit, the student uses a 0.1-F capacitance in series with Rx) and fi nds that f23 dB 5 884 kHz, what is the value of Cx? What is the value of rest?