| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit having a large input impedance. SOLUTION: A resistor R1 is connected in between transistors 1, 2, whose gate electrodes are respectively connected to a positive and a negative input terminals. Currents, having the same value, are passed to both ends of the resistor R1 by constant current sources 10, 11. The voltage at the positive and negative input terminals are the same as the voltage of both the ends of the resistor R1. The current, flowing through the resistor R1, is extracted by using current mirror transistors 4, 6 and current mirror transistors 3, 5, 7, 8. Since a current having the same value as that in the resistor R1 flows through the resistor R2, a voltage (potential difference between the positive and negative input terminals multiplied by R2/R1) is outputted to an output terminal. Since the positive and negative input terminals are connected to the gate electrodes of the transistors, the circuit has a large impedance.
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