| 摘要 |
PURPOSE:To obtain the variable resistor with linear resistance value change without mechanical construction, by forming two active elements on one pellet and obtaining the impedance in proportion to the output potential of the integrator from one of the active elements. CONSTITUTION:Two transistors TrQ1, Q2 having almost equal characteristics are formed on one pellet to constitute the integrator from FET type operational amplifier OP1, capacitor C and resistor R, and the negative feedback amplifier is constituted with the operational amplifier OP2 and TrQ1. The bias voltage E is given to the non-inverting input of the amplifier OP1 and the switch S2 is closed to -V, then the potential Vc at the point c is E+(V/CR)t after t hours. When the constant current I flows to the base of TrQ1 so that the output potential of the amplifier OP2 is Vd=Vc, the internal impedance ZQ1 of TrQ1 is Vd/I and since TrQ2 has the same characteristics as TrQ1, the internal impedance ZQ2 is equal to ZQ1 and the impedance according to the output voltage Vc of the integrator is obtained at the output Zout. The switch S2 is positioned to +V when the impedance is lowered. |
