| 摘要 |
The disclosed operational amplifier comprises a first pair of complementary type transistors that have their emitter-collector paths connected in series across a source of reference potential. The emitters of the transistors are connected together and to an output terminal. A feedback resistance is coupled from the output terminal to the amplifier input. A second pair of complementary type transistors are similarly connected across said reference potential, with the emitters thereof connected together and to a second output terminal. A second feedback resistance is coupled from the second output to the amplifier input. A pair of resistors of predetermined values are respectively connected between the base electrodes of similar type transistors of the first and second transistor pairs. And a pair of constant current sources are respectively coupled to the base electrodes of the second pair of transistors. The second pair of transistors are reversed biased until the output voltage from the first pair of transistors equals or exceeds the voltage drop across at least one of the base coupled resistors, at which time the second feedback resistance is effectively switched in shunt with the first-mentioned feedback resistance. Additional switched outputs are readily obtained with little additional circuitry.
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