International Business Machines Corporation

Maxim Integrated Products, Inc.

Daniel Shkap

Jean-Marc Roger Mourant

Amit Burstein

Tao Liang

James Francis Imbornone

A voltage mode logarithmic amplifier comprising: a first gain stage for providing an amplified rectified voltage signal responsive to an input voltage signal; a second gain stage for providing a further amplified rectified signal responsive to the input voltage signal; and an output node for producing an output voltage signal responsive to the amplified rectified voltage signal and the further amplified rectified voltage signal. The amplifier further includes: a self-biased replica stage operative to provide a voltage offset signal responsive to temperature; and a differential amplifier operative to receive the voltage offset signal and provide a temperature corrected output voltage signal responsive to the input voltage signal, wherein the differential amplifier is communicatively coupled to both the first gain stage and the second gain stage.

Logarithmic amplifier with temperature compensated detection scheme

The present invention is directed to a variable gain amplifier that may be used in RF telecommunication applications to obtain amplification of analog signals. It is also directed toward minimizing the effect that temperature variations have on the gain of the amplifier. A variable gain RF amplifier, according to this invention, has a differential amplifier and a gain control circuit. The gain control circuit has multiple transistors configured to affect a linear, variable resistor and to substantially distribute a uniform voltage potential across each transistor of the effective variable resistor.

Variable gain RF amplifier

This invention relates to a gain stage of a differential amplifier used in an intermediate frequency, voltage gain amplifier to producing a substantially linear, differential output signal for both small and large differential input signals. The invention comprises a gain regulation means in parallel with a pair of transistors forming a differential amplifier. Each transistor of the pair is connected to a first terminal of a power source through a separate impedance element. A current source connects the pair of transistors to a second terminal of the power source. The gain regulation means is connected between the first terminal of the power source and the current source such that it may develop a voltage potential between the first terminal of the power supply and the current source that varies linearly in response to an input signal.

Transistor amplifier that accommodates large input signals

The invention relates to a device for transitioning a bandgap reference circuit to its operational mode, of supplying a reference voltage, when power is supplied to the combined circuits. The device is comprised of a supply-independent biasing circuit that is electrically connected to a start-up circuit and supports the start-up circuit's ability to cause a bandgap reference circuit to transition to its operational mode for any supply voltage that supports the bandgap reference circuit's operational mode.

Bandgap reference voltage startup circuit

A balun transformer having two series connected transformers with each having a primary loop conductor disposed in a stacked configuration. One portion of each primary loop conductors is in a first layer and these two portions of the two primary loop conductors are connected in series. The second portions of the primary loop conductors are in a second layer that is spaced from the first layer with the secondary loop conductors interlaced with these portions of the primary loop conductors in the second layer.

Substrate shielded multilayer balun transformer

A multipurpose current source for generating a current with linear positive temperature dependence at a predetermined slope. This multipurpose current source includes a proportional to absolute temperature (PTAT) current source, a constant current generation circuit coupled to the PTAT current source circuit and a circuit coupled to the PTAT current source circuit and the constant current generation circuit by which a temperature dependent current developed by the PTAT current source and a constant current independent of temperature developed by the constant current generation circuit are combined The linear positive temperature dependent current is generated by subtracting to develop a temperature dependent current by reducing the temperature dependent current developed by the PTAT current source by the constant current independent of temperature developed by the constant current generation circuit.

Apparatus and method for generating current linearly dependent on temperature

An oscillator circuit having improved long term and short term phase stability. A source follower provides a signal to a bipolar transistor. The bipolar transistor is fed with a current from a current mirror which may be selectively controlled. A piezoelectric crystal and a high resistance element are connected in parallel from the collector of the bipolar transistor to the input of the source follower. The drive voltage to the piezoelectric crystal is controlled by the current mirror to improve long term frequency stability.

Low power crystal oscillator having improved long term and short term stability

The invention relates to a voltage regulator providing high immunity to DC variations of a power supply. The voltage regulator comprises a voltage regulator circuit, a gain stage that is connected to the output of the voltage regulator circuit, and a voltage modulation device forming a signal feedback loop between an output and an input of the gain stage. An initial reference voltage is generated by the voltage regulator circuit and provided to an input of the gain stage. The difference between this initial reference voltage and a fractional portion of the feedback signal, from the voltage modulation device, is amplified by the gain stage. The amplified signal of the gain stage is used to modulate the reference voltage provided to an external load. Better DC accuracy and stability is obtained by using a two stage amplifier to increase the loop gain of the voltage regulator.

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Cambridge, MA, United States of America

Daniel Shkap