Lucent Technologies Inc.

Alcatel-lucent USA Inc.

Venugopal Gopinathan

Maurice J Tarsia

John M Khoury

Vladimir Ivanov Prodanov

David Esley Long

Thi-Hong-Ha Vuong

John Paul Mattia

Robert C Melville

Peter R Kinget

Ali Eshraghi

John Michael Khoury

The specification describes MOS transistors for analog functions which have increased output impedance. The increased output impedance is the result of reduced drain depletion width. This is accomplished without adverse effects on other device parameters. The MOS transistor structures have an implant added to the lightly doped drain (LDD) with a conductivity type opposite to that of the LDD and a doping level higher than the channel doping. The added implant confines the spread of the depletion layer and reduces its width. A relatively small confinement results in a significant increase in output impedance of the device, and a corresponding increase in transistor gain.

Analog MOSFET devices

A feed-forward compensated negative feedback circuit comprises an operational amplifier having an inverting and a non-inverting input and an output. A feedback element is connected between the output of the operational amplifier and its inverting input to form a negative feedback loop. The inverting input of the op-amp is driven with a first transconductance amplifier which produces an output current proportional to an input voltage. A feed-forward transconductance amplifier receives the input voltage and produces an inverted output current proportional to the input voltage. A feed-forward current is injected at the output of the operational amplifier. By providing at the output of the op-amp the current it would be required to carry over the feedback loop, a voltage differential at the op-amp inputs is avoided, thus eliminating parasitic current flows across the parasitic input capacitance and thereby improving the circuits overall performance. In a second embodiment of the invention, a unity-gain buffer is included in the feedback loop to produce a unidirectional path. To reduce the power requirements of the buffer, a feed-forward current is injected at a point between the feedback impedance element and the unity-gain feedback buffer such that the buffer does not need to source any current through the impedance element.

Feed-forward compensation scheme for feedback circuits

A high speed and low power digital circuit for producing an output responsive to a plurality of input data signals, such as a multiplexer or a latch includes one or more data switching elements. Each of the switching elements is a differential transistor pair having one transistor driven by a control signal and the other transistor driven by a data signal. The signal levels for the data and control signals are interleaved so that each control signal turns on and off the effect of the data signal on the current flow in the switching element. The circuit structure avoids emitter coupling more than two transistors at any point in order to reduce the capacitance at critical nodes and consequently increase switching speed. By providing two switching elements with data transistors connected to a common pull-down resistor, two data signals, and a complementary pair of control signals, a multiplexing function can be performed. A second pair of similarly connected switching elements can be provided and supplied with inverted input data signals to provide complementary data output signals. The output signals can be cross-coupled to one complementary pair of data inputs to form a high speed, low voltage latch.

Low voltage high speed multiplexer and latch

Two or more equal amplitude periodic output signals which are mutually shifted in phase by an integer fraction of 360 degrees, such as 90&deg;, are generated by injection locking a ring type oscillator circuit arrangement with a periodic low phase noise signal source. More particularly, a first ring oscillator is injection locked by a low phase noise signal source, one having a noise characteristic which meets the GSM radio standard of at least &minus;132 dBc/Hz at a 3 MHz offset. An identical second ring oscillator is then driven with the output of the first ring oscillator. In one circuit configuration, an even numbered, e.g., a four stage ring oscillator is injection locked to a low-phase noise oscillator having a predetermined noise specification which is application specific and wherein a second even numbered stage, e.g., a four stage ring oscillator is coupled to the first ring oscillator. In a second circuit configuration, a first odd numbered, e.g., three stage ring oscillator, is injection locked to a low phase-noise oscillator and a second odd numbered, e.g., three stage ring oscillator, is injection locked to the first ring oscillator.

Injection locked multi-phase signal generator

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Basking Ridge, NJ, United States of America

Venugopal Gopinathan