The basic form of frequency equalization circuit

Vf in the figure is the feedback voltage, which is taken from the output voltage Vo through the EQ network . Input voltage, i and Vf are subtracted to obtain the pure input voltage Vdjo. This circuit belongs to voltage series negative feedback, and the feedback coefficient is B- Vf/Vo=REI/ Zm+REIo. ZEQ is the total characteristic impedance of the frequency equalization network . When the circuit does not add negative feedback, Vf=OV, V&= vi', the voltage amplification factor at this time is the point V- Vo/Vdi.