Stmicroelectronics S.r.l.

Sgs-Thomson Microelectronics S.r.l.

Giampiero Montagna

Andrea Baschirotto

Rinaldo Castello

Paolo Cusinato

Guido Brasca

Simone Erba

Mario Valla

An analog multiplier for multiplying a first analog voltage signal at a first frequency by a second analog voltage signal at a second frequency, comprising a first stage for converting the first analog voltage signal into a first and a second current signals, and a second stage comprising a first and a second cross-coupled current-switching pairs, driven by the second voltage signal, the first and second current-switching pairs having respective current inputs for receiving the first and the second current signals, respectively. Parasitic capacitances are inherently associated with each current input of the current-switching pairs. A compensation circuit is coupled to the current inputs of the current-switching pairs for compensating the parasitic capacitances.

Low-noise, high-linearity analog multiplier

A switched operational amplifier with fully differential topology, alternately switchable on and off, and a control circuit. The operational amplifier has a first differential output ( ) and a second differential output, and a control terminal. The control circuit includes a capacitive detecting network including a first capacitor and a second capacitor connected between the first and second differential outputs and a common-mode node, and a third capacitor connected between the common-mode node and ground in a first operative condition, and between the common-mode node and the supply voltage in a second operative condition. A control transistor is connected between the common-mode node and the control terminal of the operational amplifier and supplies a control current correlated to the voltage on the common-mode node. A switchable voltage source, connected to the common-mode node, supplies a desired voltage in a first operative condition, when the operational amplifier is off.

Fully differential, switched capacitor, operational amplifier circuit with common-mode controlled output

A switched input circuit structure of the type which includes an input terminal receiving an input voltage and an output terminal connected to an input capacitor. An operational amplifier is included having a non-inverting terminal connected to a ground reference terminal, an inverting input terminal, and an output terminal feedback connected to the inverting input terminal and held in a virtual ground condition by a parallel of first and second charge paths which are connected between the input terminal of the switched input circuit structure and the inverting input terminal of the operational amplifier and connected to the supply voltage reference and the ground reference, respectively.

Switched input circuit structure

Growing community of inventors

Tortona, Italy

Giampiero Montagna