| 摘要 |
PURPOSE:To correct the drift by adding a signal obtained from a load resistor of a noninverting amplifier vacuum tube of the cathode follower stage and an inverted signal from a load resistor of an inverting amplifier vacuum tube and feeding back the result to an inverting input of the input stage. CONSTITUTION:The load resistor for vacuum tubes V3a, V3b is divided into resistors R1-R4 for voltage division. The relation of R1=R4 and R2 exists and the resistors R3 and R4 are selected so that the AC and DC voltage at a voltage division point is within a permissible input voltage of an inverse amplifier connected next. A variable resistor VR is inserted between the resistors R2 and R3 for the purpose of correcting it if a DC unbalance takes place, its sliding point is connected to ground and the connecting point of the resistors R3 and R4 is connected to the input of an inverting amplifier OP1 whose gain is the unity. The common connecting point of the resistors R1 and R2 is connected directly to a summing node and the common connecting point of the resistors R3 and R4 is connected directly to a summing node via the inverting amplifier OP1 and further connected to the input of a filter F. The output of the filter F is connected to the inverting input of the 1st stage via a voltage follower OP2.
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