Analog Devices International Unlimited Company

Linear Technology Corporation

Gregory A Fung

Joseph Adut

Brian D Hamilton

Jeremy Wong

Eugene Cheung

Voltage-to-current converters that include two current mirrors are disclosed. In an example voltage-to-current converter each current mirror is a complementary current mirror in that one of its input and output transistors is a P-type transistor and the other one is an N-type transistor. Such voltage-to-current converters may be implemented using bipolar technology, CMOS technology, or a combination of bipolar and CMOS technologies, and may be made sufficiently compact and accurate while operating at sufficiently low voltages and consuming limited power.

Voltage-to-current converter with complementary current mirrors

A multi-stage transimpedance amplifier (TIA) with an adjustable input linear range is disclosed. The TIA includes a first stage, configured to convert a single-ended current signal from an optical sensor of a receiver signal chain to a single-ended voltage signal, and a second stage, configured to convert the single-ended voltage signal provided by the first stage to a differential signal. In such a TIA, the input linear range may be adjusted using a clamp that is programmable with an output offset current to keep the second stage of the TIA from overloading and to maintain a linear transfer function without compression.

Transimpedance amplifiers with adjustable input range

An example analog signal multiplexer includes two differential input signal ports for receiving a first and a second differential input signals, INand IN. The multiplexer further includes a differential output signal port with two output terminals OUT+ and OUT&#x2212;, for outputting a signal based on one or more of the input signals INand IN. Furthermore, the multiplexer includes a pair of load elements, and an additional differential output signal port that has two output terminals TERM+ and TERM&#x2212;. The load elements are not coupled directly to the output terminals OUT+ and OUT&#x2212;, but, rather, are coupled to the output terminals of the additional output signal port, TERM+ and TERM&#x2212;, enabling a modular approach where multiple instances of the multiplexer may be combined on an 'as-needed' basis to realize multiplexing between a larger number of differential inputs that a single multiplexer would allow.

Modular analog signal multiplexers for differential signals

Differential clamp circuits configured to recirculate the current in one clamp, either low-side clamp or high-side clamp, from one output of a differential signal to the other output of the differential signal are disclosed. Differential clamp circuits described herein may be particularly suitable for providing programmable clamps at differential outputs of an ADC driver and may be particularly beneficial to implement clamps that are symmetrical around an ADC's input common-mode voltage. Some differential clamp circuit described herein may advantageously present a smaller capacitive load at each output, thus reducing bandwidth degradation of the output stage. Furthermore, differential clamp circuits described herein may operate with only one control voltage, making it easier to limit the output excursions symmetrically around the default common-mode voltage.

Differential clamp circuits with current recirculation

An actual linear amplifier distorts an input signal, such as an RF signal, and generates third order intermodulation (IM3) products. In an embodiment of a Class A amplifier, the linear amplifier is a bipolar, common emitter-configured (CE) transistor using a cascode transistor to provide a fixed collector bias voltage to the CE transistor. The CE transistor has a transconductance vs. base-emitter voltage (V) characteristic which, when plotted, shows a transconductance that increases with an increasing Vto a maximum, then drops, then tapers off, wherein there is an inflection point between the maximum transconductance and where the transconductance tapers off. A DC bias circuit provides a DC bias voltage to the base of the CE transistor that causes the CE transistor's operating point to track the inflection point over a range of temperatures. This operating point causes the IM3 products to be greatly reduced.

Bias point setting for third order linearity optimization of class A amplifier

An actual linear amplifier distorts an input signal, such as an RF signal, and generates third order intermodulation (IM3) products. A single-port predistortion circuit is connected at a single node of an input line to the amplifier via an AC coupling capacitor. The fundamental frequency of the input signal is applied to a forward biased diode junction. The current through the diode is applied to a second capacitor. The appropriate setting of a tuning device, such as a tunable resistor or a tunable capacitor, causes the predistortion circuit to invert the second harmonic generated by the diode. The inverted second harmonic signal is applied to the single node of the input line to add predistortion to the signal applied to the amplifier. The predistortion cancels or substantially reduces the IM3 products at the output of the amplifier.

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Fremont, CA, United States of America

Gregory A Fung