| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize and especially thin a Wien-Bridge oscillation circuit. SOLUTION: The circuit is provided with a first operand amplifier 1, a first impedance means for deciding oscillation frequency 2, which is connected between the noninverting input terminal and the output terminal of the first operand amplifier 1, a second impedance means for deciding frequency 3, which is connected between the noninverting input terminal and ground, a third impedance means for deciding oscillation amplitude 4, which is connected between the inverting input terminal and the output terminal of the first operand amplifier 1, and a fourth impedance means for deciding oscillation amplitude 5, which is connected to the inverting input terminal and ground. A variable resistor 2a is arranged in the first impedance means 2 or the second impedance means 3 and FET 3a is disposed in the other means. The current value of first FET3a is changed in cooperation with the resistance value change of the variable resistor 2a and the direction of the increase/decrease of a resistance value is made opposite to that of the current value.
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