| 摘要 |
PURPOSE:To switch an output impedance, by constituting a collector resistor of one of a pair of transistors (TRs) driving a load with pulse through resistors in parallel connection and inserting a switching element to one of the resistors. CONSTITUTION:TRs 10 and 11 constitute a current switching circuit, the emitter is connected in common to the collector of a TR13, and the base is connected to an output of different phase of a predriver circuit 12, and a current can alternately flow by inputting a pulse to the circuit 12. The TR13 constitute a constant current source with an operational amplifier 14. The collector of the TRs 10 and 11 is connected to the emitter of a TR16 via resistors R15 and 18, and a series circuit consisting of an R19, a distributed constant line 20 and a relay 21 is connected between the collector of the TR10 and the emitter of the TR16. The TR16 constitutes a constant voltage source with an operational amplifier 17. A load 24 is connected to an output point 22 via a distributed constant line 23. A load with different impedance can be driven by switching the relay 21. |
