SIGNAL PROCESSING CIRCUIT WITH VARIABLE GAIN INPUT STAGE

摘要

PURPOSE: To prevent the occurrence of disturbance of a signal by a transitional condition after variable gain is changed by correcting a value of a state variable so as to be in direct proportion to correction of an amplification/attenuation factor. CONSTITUTION: A signal to be processed is supplied to input of a first variable gain stage 4 to perform amplification/attenuation by a line 10, and the stage 4 sends out an amplitude-standardized signal to a line 12 as output in response to an inputted signal. The stage 4 is controlled by a gain control means 6. A signal processing circuit 2 sends out a processed signal to a line 14 as output. A line 16 adds a signal supplied from the processing circuit 2 to the gain control means 6 so as to change gain of the stage 4. Two lines 18 and 20 respectively supply control signals to the stages 4 and 8. The stages 4 and 8 respectively change its gain in response to these. That is, a value of a state variable is corrected so as to be in direct proportion to correction of an amplification/ attenuation factor, and a transitional condition is restrained.