Output voltage controlled impedance output buffer

摘要

The present invention concerns an output buffer, which overcomes previous disadvantages of driving transmission line loads by providing a variable output impedance in response to the load on the output. The buffer generally comprises a pullup device for providing a high voltage at the output in response to a first input, a pulldown device configured to provide a low voltage at the output in response to a second input and a second pulldown device configured to provide additional low drive at the output. The second pulldown device provides an impedance at the output which varies with respect to the voltage present at the output.