| 摘要 |
A bistable switching circuit includes a transistor differential pair coupled to a current Schmitt trigger circuit. The Schmitt trigger circuit includes a pair of cross-coupled transistors, one of which has unity current gain and the other of which has current gain greater than unity, and an output transistor coupled to the unity gain transistor. A resistor is connected in series with each of the cross coupled transistors, one of the resistors being in series with the output transistor. The circuit arrangement is such that no output current is present until the cross-coupled transistors are fully regenerating, the condition occurring when the differential input voltage is at balance. The resistor in series with the output transistor provides an extra margin of safety in this regard by lowering the VBE of the output transistor to keep it off at the time when regeneration is starting to occur.
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