Integrated op amp tone control circuit

The integrated operational amplifier circuit has the characteristics of high voltage gain and high input impedance. Using it to make a tone control circuit has
the advantages of simple circuit structure and stable operation. Figure 4-5 is the current analysis of the tone control circuit composed of integrated operational amplifiers. It is as follows: at low frequency , cl.C2 can be regarded as an open circuit, so there is:     Maximum improvement amount of low frequency: Avra; = (Ri + RPl);     low frequency Maximum attenuation: Avc=Rl/(RI+Rpt); low-frequency cutoff frequency: Ll - 1/2,arRPlCl o (unit: one ratio, R - fl (Europe), CF (French))