High to low transition speed up circuit for TTL-type gates.

摘要

The specification discloses an input transistor (14) which Is variable between high and low impedance states in response to input voltage transitions at terminal 10. An output transistor (16) is coupled to the input transistor (14) and is responsive to an input transition at terminal 10 for changing impedance states. Circuitry including a speed up transistor (44) is coupled between the input transistor (14) and output transistor (16) for applying added current to the output transistor (16) to speed the change of impedance stste. The circuitry applies added current to output transistor (15) until the output voltage at terminal (18) falls below twice the base-emitter voltage of the output transistor (16).