Low-noise transmission line termination circuitry

Claim 1

For use in a computer circuit, the combination comprising: an integrated circuit chip having an input for receiving a binary input signal; and transmission line termination circuitry included on said integrated circuit chip and coupled to said input for reducing noise occurring when a binary signal is transmitted to said input; said transmission line termination circuitry comprising a first constant current source, a second constant current source, and a switchable current steering switch, said first current source being coupled to said input so as to provide a DC load at said input for an applied signal, and said second current source being coupled to said input via said switchable current steering switch for setting clamping current for a transition of said binary signal; said first current source including a first transistor coupled between a current supply voltage and said input, said second current source including a second transistor coupled between said current supply voltage and said current switch, and each of said first and second transistors including a control terminal coupled to a control voltage source; said switchable current steering switch being operative to switch in response to said binary input signal rising to a predetermined level so as to cause the input signal to see a step increase in load current as it increases above said predetermined level.