Analog Devices,inc.

Tektronix, Inc.

Barrie Gilbert

Todd C Weigandt

John Cowles

Eberhard Brunner

Shao-Feng Shu

Adrian P Brokaw

Peter R Holloway

Jonathan Mark Audy

Sukhjinder S Deo

Daryl Carbonari

Fred Weiss

A device has at least two current mode logarithmic amplifiers having currents as their inputs, and multiplexing logic electrically connected to outputs of the current mode logarithmic amplifiers to select one of the current mode amplifiers to produce an output signal.

Instrumentation log amp with multiplexed inputs

A hybrid, translinear amplifier has at least one gain stage including first and second gain transistors, at least a first load transistor electrically coupled to the first gain transistor and at least a second load transistor electrically coupled to the second gain transistor, and load resistors electrically coupled to the load transistors. A hybrid, translinear amplifier with selectable gain has a first hybrid, translinear amplifier cell having at least first and second load transistors, each load transistor having a load resistor, at least one additional hybrid, translinear amplifier cell having at least third, fourth, fifth and sixth load transistors, each load transistor having a load resistor, at least two switches electrically coupled to the amplifier cells to allow selection of one of the amplifier cells, and a differential output signal having a gain corresponding to a selected amplifier cell.

Hybrid translinear amplifier

A radio frequency diode detector has a set of diodes having a differential voltage output, and a current source electrically coupled to the ring of diodes, the current source coupled to provide a forward bias current. This is followed by nonlinear signal processing to create an overall linear detector suitable for use in microwave power measurement.

Microwave voltmeter using fully-linearized diode detector

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

A variable gain amplifier has an attenuator having an input and a series of tap points, and a series of low-inertia switches, each switch coupled to a corresponding one of the tap points to steer outputs from the attenuator to an output terminal. An amplifier has an input cell, a load coupled to an output of the input cell, a buffer having an input coupled to the load, a feedback network coupled between an output of the buffer and the input cell, and a variable filter cell coupled to the input cell.

Instrumentation input systems

Variable attenuation systems having continuous input steering may be used to implement vector or quadrature modulators and vector multipliers. Discrete implementations of attenuators with continuous input steering may have two outputs which may be cross-connected to provide four-quadrant operation. A symmetrically driven center tap may provide improved zero-point accuracy.

Vector modulator having attenuators with continuous input steering

An input stage for an instrumentation system may include a resistor coupled between an input terminal and a summing node, and an amplifier arranged to maintain the voltage at the summing node. In anther embodiment, an instrumentation input system may include an input stage to receive a signal to be measured, and a variable gain amplifier having an input coupled to an output of the input stage, wherein the variable gain amplifier comprises two or more gain stages. A variable gain amplifier may include an attenuator having an input and a series of tap points and a series of low-inertia switches to steer outputs from the attenuator to an output terminal.

An amplifier having an imbalance between pull-up and pull-down sections may include a counterpart section to balance the output sections and/or enable them to be driven by balanced drive signals. In one embodiment, a rail-to-rail output stage may include a current minor to drive one side of the circuit. The other side may be driven by a transistor having a counterpart transistor to balance the circuit. A drive section may include a balance point to facilitate balancing the drive signals.

Rail-to-rail output stage with balanced drive

A measurement system includes a detector to generate a measurement signal responsive to an input signal, and a nulling circuit coupled to the detector to generate a control signal responsive to the difference between the measurement signal and a set-point signal. The nulling circuit may include a bandwidth compensation stage to maintain the overall control loop bandwidth at a substantially constant value.

Detector with bandwidth compensation

An embodiment of a logarithmic circuit may include a logging transistor, a guard circuit arranged to force an input current into an input terminal of the logging transistor, and a positioning circuit arranged to maintain a voltage of the logging transistor. The guard and positioning circuits may include first and second feedback loops, respectively. Another embodiment of a logarithmic circuit may include a logging transistor arranged to generate a logarithmic output in response to an input current, and a feedback loop arranged to provide adaptive compensation to the logging transistor. The feedback loop may be arranged to provide compensation in response to the magnitude of the input current. Another embodiment of a logarithmic circuit may include first and second logging transistors having collectors arranged to receive input currents, and first and second feedback amplifier arranged to drive emitters of the logging transistors.

Logarithmic circuits

An RF measurement system includes an envelope detector to extract the modulation envelope of the RF input signal. The resulting baseband envelope signal is then applied to a statistics extraction circuit which provides a precise measure of the modulation envelope. The statistics extraction circuit can be implemented with any number of lower-frequency precision measurement technologies because the high-frequency carrier portion of the signal is removed, and thus, the demands on the post-envelope extraction circuit are greatly reduced. In one embodiment, the envelope detector and statistics extraction circuit may be implemented as a logarithmic amplifier followed by an RMS-responding post-processing circuit to provide accurate power measurement. Because the envelope signal is represented in the logarithmic domain, the square-law function required for RMS conversion can be accomplished by scaling the envelope signal by an appropriate factor before introducing it into a translinear loop in the RMS post-processing circuit.

Measurement systems with envelope pre-detection

An input stage receives a differential input signal at first and second input nodes and provides a differential output current at first and second output nodes. The differential output current includes a component taken from the input nodes through first and second impedances, and an additional component generated in response to a sample of the voltage of the differential input signal. A transconductance cell having cross-coupled inputs may generate the additional component of the output current.

Output stage with adaptive bias control

A selectable gain amplifier includes two or more selectable gain stages, each gain stage having a first input coupled to receive an input signal, a second input, and an output. The amplifier further includes and two or more feedback paths coupled between the outputs and the second inputs of the selectable gain stages.

Post amplifier with selectable gain

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.

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Portland, OR, United States of America

Barrie Gilbert