Abstract
A telephone chip that performs all the basic functions of a speech circuit using only two external components is reported. Precision filtering based on switched-capacitor (SC) techniques is used to implement on-chip impedance termination, hybrid with sidetone cancellation, and DC characteristics starting from a single 1% external resistor. A new low-drop on-chip voltage supply generator derived from the line using an external storage capacitor is also realized. Better than 33-dB impedance matching and more than 30-dB sidetone cancellation is achieved without any external trimming. The TX linearity is better than 50 dB up to 4.4 V/sub p-p/ on the line. The chip has an active area of approximately 2.6 mm/sup 2/ and draws 1.5 mA of quiescent current.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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