3. (15%) Fig. 3 shows a circuit that performs a low-pass STC function. Such a circuit is known asa first-order low-pass active filt er. Derive the transfer functi on, the dc gain and the 3-dBfrequency. Design the circuit to ob tain an input resistance of 1k Ω, a dc gain of 20dB, and a 3dBfrequency of 4kHz. At what frequency does the magnitude of the transf er function reduce tounity?