DC input circuit with controlled leakage current

摘要

A DC input circuit provides a digital output dependent on an input voltage spanning a low range and a high range. A first transistor current source provides a bounded leakage current for a low range voltage. A parallel transistor current source in series with a voltage breakdown diode provides a second constant current path for high range voltages through a current sensitive switch. The total input current is thus limited, thereby reducing heat dissipation.