| 摘要 |
PURPOSE:To facilitate the adjustment of the resonance frequency of an impedance circuit with a small-sized constitution, by connecting a reference point of the impedance circuit directly to the other end of a load current detecting resistance whose one end is grounded and supplying the voltage of a power source based on a prescribed reference potential point to an active element. CONSTITUTION:A power supply device 19 which supplies DC voltages +B1 and -B1 to an amplifier 1 is provided, and these DC voltages are supplied to the cathode of a Zener diode 31 and the anode of a Zener diode 32 through constant current sources 29 and 30 respectively and are converted to DC voltages +B2 and -B2 and are sent to operational amplifiers 13 and 14. When a middle point C of voltages + or -B2 is not grounded but is connected to a point A, the terminal A is grounded through a load current detecting resistance 5 to become the potential reference point of an impedance converter 11. When resistance values of resistances 12, 15, 16, and 18 and the capacity of a capacitor 17 are denoted as R12, R15, R16, R18, and C17 respectively, an impedance ZAB between points A and B of the converter 11 is expressed by an equation 1, and the equation is transformed to ZAB=jomegaC17.R12.R16.R18/R15. Thus, the converter 11 becomes equivalent to a circuit consisting of only an inductance. |
