BASE CURRENT COMPENSATING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To cancel the offset that is caused by a 2nd current when the collector-emitter withstand voltage of a transistor TR is set at a low level and no input signal exists by setting a 1st current to compensate the base current of the relevant TR and accordingly securing the same voltage drop level between the 1st and 2nd resistors. SOLUTION: One of both ends of a resistor 6 of resistance value R1 is connected to an IC terminal 3 of a signal source 1 with the other end of the resistor 6 connected to one of both ends of a resistor 7 of resistance value R2 respectively. Meanwhile, the other end of the resistor 7 is connected to a voltage source 8 of a bias circuit 30. Then a current of current value IC is supplied to the circuit 30 to compensate the base current of a TR 9 which flows into/out of the connecting point of both resistors 6 and 7. The relation of R1/R2=|(IC-IB)/ IB|is secured between the current value IC and the current value IB which flows into/out of the connecting point of the terminal 3 and a differential input buffer 32 where the negative feedback is applied to one of its both input terminals. As a result, the base current is compensated for the TR 9.