VARIABLE GAIN AMPLIFIER

摘要

PURPOSE:To obtain a variable gain correcting the speed in an excellent way by bringing each feedback resistor Ri of a variable gain amplifier generating a speed control correcting signal of a magnetic head into an R1/2 and providing a correction resistor between the input and output. CONSTITUTION:The variable gain amplifier for driving a magnetic head obtaining a correction signal F for an object signal from an analog error signal E and program digital signals D1-D8 is constituted by using a feedback inversion amplifier 5 to which an error signal E is impressed via an input resistor Rs, bringing the value of feedback resistors R1-R8 into Ri=R1/2i-1 with a bit of a program digital signal so as to make it inversely proportional to the weight of bit and providing a correction resistor (not shown in a figure) between the input and output of the amplifier thereby varying properly the gain and driving stably the magnetic head.