| 摘要 |
A voltage comparator is provided with a high speed output stage having positive feedback. The output stage uses two transistors, both in grounded emitter circuit configurations, and two current sources supplying current to two different nodes associated with the two transistors. One node is connected to the base of a first one of the two transistors and to the collector of the second transistor. The other node is at the junction of the base of the second transistor and a resistor connected to the collector of the first transistor. An input comparator circuit selectively diverts current from the base of the second transistor. When the current is diverted from the base of the second transistor, the first transistor is turned on and the second transistor is turned off, as its base is starved of any drive. When the input voltage changes so that the current is no longer diverted, current is supplied first through the resistor to the collector of the first transistor and then to the base of the second transistor. The voltage at the base rises rapidly to turn on the second transistor and at the same time the declining collector-to-emitter voltage of the second transistor reduces the base voltage at the first transistor so it quickly turns off. The circuit is compatible with Integrated Injection Logic (I2L), and other logic systems.
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