| 摘要 |
A device for converting binary logic pulses into an output current and the output current being switchable between a positive and negative polarity. The device provides a charge pump circuit which is suitable for the phase-detector stage in a phase-locked loop (PLL) circuit. The charge pump circuit comprises an input stage for the "UP" binary logic pulses and a second stage for the "DOWN" binary logic pulses. The input stages comprise emitted-coupled transistor pairs. The circuit includes current sources and current sinks for generating the output current in the input stages in response to the binary logic pulses. The circuit features a pair of commutating diodes between the outputs of the input stages. The commutating diodes control the output current and the leakage current in the idle state. The circuit also includes a clamping circuit to limit the voltage swing across the commutating diodes. The charge pump circuit according to the present invention exhibits a fast response time, a symmetrical response to the binary logic pulses, and virtually zero leakage current in the idle state. The charge pump circuit utilizes non-complimentary bipolar processes and is suitable for a monolithic integrated circuit implementation.
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