Maxim Integrated Products, Inc.

Scott Lindsey Williams

Martin Tomasz

Benjamin J McCarroll

James W Marsh

James W H Marsh

The present invention discloses a method and apparatus for correcting the DC offset caused by self-conversion of the oscillator signal in an RF-to-baseband converter. The circuit comprises: a subtractor for subtracting an amplified DC offset signal from a filtered mixer signal to generate a corrected signal; a baseband amplifier coupled to the subtractor to receive the corrected signal to generate a baseband output signal; a low-pass filter coupled to the baseband amplifier to generate a DC offset signal representative of the DC offset; and a DC offset amplifier coupled to the low-pass filter and the subtractor to generate the amplified DC offset signal.

DC offset correction for direct conversion tuner IC

A variable gain amplifier having improved bandwidth and linearity, and having improved dynamic range by allowing the amplifier to be designed for low noise performance, while retaining the linearity normally lost with low noise designs. The amplifier is of the current steering type, having a differential current steering input stage coupled to a further current steering stage for controlling the gain responsive to a gain control signal. Current is maintained in a pair of common base connected transistors in the output circuit so that these transistors do not create excessive noise or limit the bandwidth and linearity of the amplifier at low gain. Maintaining the current in these transistors responsive to the gain control signal may maintain a substantially constant current in these transistors independent of gain. Exemplary embodiments are disclosed.

Variable gain amplifier with improved linearity and bandwidth

A phase detector biased in a manner to alleviate the mismatch between the biasing current sources and the phase detector core bias currents. The bias setting resistors are coupled together at a common node that forms the negative input of a differential feedback amplifier. The positive input to the amplifier is referenced to a reference voltage, and the output of the amplifier controls the biasing current sources. The feedback amplifier forces the average voltage at the current source outputs to approximately match the reference voltage applied to its positive input. Thus the average bias current from the bias current sources is forced to track the average bias currents of the phase detector core.

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Tigard, OR, United States of America

Scott Lindsey Williams