Patent ID: 8581619

Claim:
A calibrator, comprising: a reference-level node; a first filter coupled to the reference-level node and configured to receive a reference-impedance signal; a second filter coupled to the reference-level node and configured to receive a calibration-feedback signal; and a comparator having first and second input nodes each coupled to a respective one of the first and second filters, having an output node, and configured to generate on the output node a calibration-indicator signal; the calibrator further including: a supply node; a reference-impedance node coupled to the first filter and configured to carry the reference-impedance signal; a calibration-feedback node coupled to the second filter and configured to carry the calibration-feedback signal; an amplifier having a first input configured to receive a reference signal, a second input coupled to the reference-impedance node, and an output node; a first transistor having a control node coupled to the amplifier output node and having a conduction path coupled between the supply and reference-impedance nodes; and a second transistor having a control node coupled to the amplifier output node and having a conduction path coupled between the supply and calibration-feedback nodes.