| 摘要 |
<p>A driver circuit with pull down npn transistor drives an output voltage signal in response to an input voltage signal, without high-speed pnp transistors. A first npn transistor (22) provides current to the output node when the output node is at a level equal to and less than the level of the input voltage signal less a base-to-emitter junction drop across the first npn transistor (22). A second npn transistor (20) sinks current from the output node when the output node is at a level greater than the level of the input voltage signal less the base-to-emitter junction drop across the first npn transistor (22). The second npn transistor (20) is controlled by a level of a control node (38). When the level of the output node is greater than the level of the input voltage signal less the base-to-emitter junction drop, the first npn transistor (22) is turned off and the level of the control node (38) is charged up by a current source (26). When the level of the control node (38) reaches a sufficient level, the second npn transistor (20) is turned on and the level of the output voltage signal is decreased.</p> |
