BiCMOS output circuit with static output current control circuit

摘要

In an output circuit having pull down and pull up npn transistors, a static output-current control circuit is provided. The control circuit is turned on by detecting that a potential at the output terminal of the circuit is at a predetermined value of less. When the input signal supplied to the input terminal goes from CMOS level "0" to CMOS level "1" to change the voltage at the output terminal from TTL level "1" to TTL level "0", and when the potential at the output terminal becomes a predetermined value or less, the static output-current control circuit is turned on. A base current is supplied from the static output- current control circuit to the pull down npn transistor. As a result, the static output current is not decreased but kept constant. To the contrary, when the input signal goes from CMOS level "1" to MOS level "0" to change the voltage at the output terminal from TTL level "0" to TTL level "1", and the potential at the output terminal is a predetermined value or more, the output current-control circuit is turned off, and the output current- control circuit does not have any influence on the operation of the output circuit.