| 摘要 |
PURPOSE:To apply an optimum current to a dummy load irrespective of an output voltage by providing a circuit with variable DC impedance. CONSTITUTION:The circuit consists of a transistor 15 in which a resistor 18 and a reference power source 14 is connected in series to the emitter, an operational amplifier 16, an MOSFET 17 in which output of the operational amplifier 16 is gate connected and resistors 19, 20. The operational amplifier 16 in which minus side input is connected to the source of an FET 17 can give sufficiently high input resistance to the collector circuit of the transistor 15, and can give voltage equal to voltage between terminals of the resistor 19 between terminals of the resistor 20. When input voltage of the operational amplifier 16 drops, the output voltage also drops and operation resistance of th3 FET 17 increases. Accordingly, dummy load constituted by the FET 17 and direct circuit of the resistor 20 decreases and adjusted to required load current.
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