What is the voltage gain in Fig. 36-30a? What is the cutoff frequency? What is the frequency response?
What is the voltage gain in Fig. 36-30a? What is the cutoff frequency? What is the frequency response?
This is a noninverting first-order low-pass filter. With Formulas (36-16) A_v=\frac{R_2}{R_1}+1 and (36-17), f_c=\frac{1}{2\pi R_3C_1} the voltage gain and cutoff frequencies are
A_v=\frac{39 k\Omega }{1 k\Omega}+1=40f_c=\frac{1}{2\pi (12 k\Omega)(680 pF)}=19.5 kHz
Figure 36-30b shows the frequency response. The voltage gain is 32 dB in the passband. The response breaks at 19.5 kHz and then rolls off at a rate of 20 dB per decade.