| 摘要 |
PURPOSE:To determine the angular frequency of poles of a low-pass filter according to the response time contant of an AGC system and to match the angular frequency of zero point to that of the pole of an equivalent low-pass filter of a variable resistive element, by inserting a low-pass filter in the path of a negative feedback signal. CONSTITUTION:A low-pass filter 7 is inserted to a negative feedback loop in an AGC circuit. The filter 7 consists of resistors R1-R3 and a capacitor C, and equation (3) is established between an input voltage V1 and an output voltage V0, where omegaC3 is the angular frequency of poles and omegaC2 is the angular frequency of zeros. The loop gain of the AGC circuit relating to the envelope frequency is mubeta= mubeta(0)'[1+(jomega/omegaC2)]/[1+(jomega/omegaC1)][1+(jomega/omegaC3], where mubeta(0)'=K.mubeta(0),and mubeta= mubeta(0)'/[1+(jomega+omegaC3)]is obtained by selecting as omegaC1=omegaC2, and omegaC3<omegaC1. The response time constant of system is determined with the angular frequency omegaC3 of the poles, which is independently of the time constant of a thermister 6. |
