Dallas Semiconductor Corporation

Sigmatel, Inc.

Advanced Miere Devices, Inc.

Harry S Jackson

Geoffrey E Brehmer

Michael A Margules

A method and apparatus for an oversampled single bit digital to analog convertor (DAC) is accomplished by using an FIR filter as the analog reconstruction filter, wherein the FIR filter includes primary current sourcing circuitry and secondary current sourcing circuitry. The primary current sourcing circuitry is used to produce a portion of the FIR coefficients having relatively large values, while the secondary current sourcing circuitry is used to fine tune the FIR coefficients having the relatively large values and to produce the other FIR coefficients. Combining the results of the primary current sourcing circuitry and the secondary current sourcing circuitry produces an analog signal.

Method and apparatus for an oversampled digital to analog convertor

A method and apparatus for a controlled oscillator which may be incorporated in a phase locked loop is accomplished by including a current controlled reference, a current mirror and a plurality of inverters that form a ring oscillator within the controlled oscillator. The controlled reference provides a current control signal to the current mirror, which, in turn, provides a load control signal to each inverter of the ring oscillator. Each inverter is characterized by a differential load section which includes a pair of load transistors for receiving the load control signal and for providing a current source from the load control signal and a pair of clamping transistors configured to provide a non-linear clamping circuit which limits the voltage range of a differential output. The load transistors are connected in parallel with the clamping transistors to provide a linear differential output. The load control signal dynamically regulates the impedance of the differential load section such that the controlled oscillator may stablely operate at any frequency and be produced without performance variations due to variances in the fabrication process.

Method and apparatus for a controlled oscillation that may be used in a

A fully differential non-linear amplifier includes an operational amplifier (12), a first input resistor (R1), a second input resistor (R2), a first feedback resistor (R3), a second feedback resistor (R4), a first clamping network (CN1), and a second clamping network (CN2). The first clamping network (CN1) is formed of a first P-channel clamping transistor (P10) and a first N-channel clamping transistor (N10). The second clamping network (CN2) is formed of a second P-channel clamping transistor (P12) and a second N-channel clamping transistor (N12). The gates of the first and second P-channel clamping transistors (P10, P12) are connected to receive a P-bias signal. The gates of the first and second N-channel clamping transistors (N10, N12) are connected to receive a N-bias signal. The non-linear amplifier clamps its differential output signal to a constant voltage level independent of variations in process and temperature.

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Austin, TX, United States of America

Harry S Jackson