Analog Devices,inc.

John Cowles

Barrie Gilbert

Todd C Weigandt

Sukhjinder S Deo

Filter circuits with emitter follower transistors and servo loops, and associated methods and apparatuses, are disclosed herein. In some embodiments, a filter circuit may include: a resistor-capacitor network having an input to receive an input signal; an emitter follower transistor, coupled to the resistor-capacitor network, wherein the filter circuit has an output to provide an output signal from the emitter of the emitter follower transistor; a current source to provide a constant reference current; and a current-buffering servo loop circuit, coupled to the emitter follower transistor and the current source, including a current buffer and a controlled current sink to maintain the collector current and the emitter current of the emitter follower transistor equal to the constant reference current.

Filter circuits with emitter follower transistors and servo loops

An amplifier includes an amplifier section having selectable signal paths to provide discrete gain settings, and logic to incrementally select the signal paths. The logic may be configured to increment the gain in response to digital gain control signals or an analog gain control signal. Another amplifier has an input section with one or more input cells and an output section with one or more output cells. Either the input section or the output section includes at least two cells that may be selected to provide discrete gain settings. A loop amplifier is configured in a feedback arrangement with the input section. The input and output sections may have multiple selectable cells to provide coarse and fine gain steps. The gain of the loop amplifier may be coordinated with the gain of the input section to provide constant bandwidth operation.

Incremental gain amplifier

An amplifier has an input section with one or more input cells and an output section with one or more output cells. Either the input section or the output section includes at least two cells that may be selected to provide discrete gain settings. A loop amplifier is configured in a feedback arrangement with the input section. The input and output sections may have multiple selectable cells to provide coarse and fine gain steps. The gain of the loop amplifier may be coordinated with the gain of the input section to provide constant bandwidth operation.

Amplifier having input/output cells with discrete gain steps

A peak-to-average measurement system includes an envelope detector to extract the modulation envelope of an input signal having a modulated carrier. The resulting baseband envelope signal is applied to a peak detector and an averaging circuit. In one embodiment, the averaging circuit includes a translinear core to generate a squared signal in response to the envelope signal and an RMS-average circuit to perform the averaging portion of an RMS function. The translinear core may also generate a replicated version of the envelope signal for the peak detector. The use of a common envelope detector for both the peak detector and averaging circuit may provide improved scaling accuracy.

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Beaverton, OR, United States of America

John Cowles