Patent ID: 7301366
Filing Date: 2007-11-27
Classification: H03H,H04L

Abstract:
1. A tunable impedance circuit, comprising: a primary switchable resistance circuit; a plurality of auxiliary switchable resistance circuits connected in parallel with the primary switchable resistance circuit; a tuning circuit coupled to said plurality of auxiliary switchable resistance circuits for combining at least one of said auxiliary switchable resistance circuits with at least another of said auxiliary switchable resistance circuits to produce a composite impedance; said tuning circuit including a current source for producing a current that is substantially invariant over a range of operating conditions; said tuning circuit including a control impedance coupled in series with said current source, said substantially invariant current flowing through said control impedance to produce a control voltage across said control impedance; and said tuning circuit including a logic circuit coupled to said control impedance for determining, based on said control voltage, how many of said plurality of auxiliary switchable resistance circuits are to be combined to produce said composite impedance.