| 摘要 |
<p>A transistor-transistor logic (T<2>L) circuit uses a switchable feedback network to enhance the negative-going output switching characteristics of the circuit. The switchable feedback network includes a Schottky diode (D2) in series with the collector-emitter path of a feedback transistor (Q5), connected between the output terminal (3) of the circuit and the collector zone of a phase-splitter transistor (Q1). The base zone of the feedback transistor (Q5) is connected to the intermediate node (6) of a Darlington pull-up amplifier (Q2, Q3) in the T<2>L circuit, so that the feedback network is activated only during the negative-going output transition. This configuration provides a circuit in which a superior negative-going switching transition characteristic is obtained, while at the same time preventing malfunction and possible damage to the device resulting from unwanted external current feedback.</p> |
