Sgs-Thomson Microelectronics S.r.l.

Bruno Ferrario

Mauro Fagnani

Paolo Sandri

Antonio Magazzu'

An integrated capacitance multiplier circuit utilizes a pair of field effect transistors, biased in a conducting state, as virtual resistances of a classic operational amplifier network for implementing a capacitance multiplier function. The two field effect transistors have different sizes from each other for attaining a given ON-resistance ratio. A biasing circuit provides independently adjustable biasing voltages for the two field effect transistors. At least one of the two biasing voltages produced by the biasing circuit can be made dependent on temperature according to a certain dependency law in order to exploit the capacitance multiplier circuit for temperature compensating an integrated RC circuit employing the virtual capacitance provided by the multiplier circuit.

Integrated capacitance multiplier especially for a temperature

A synchronization circuit for electronic devices and components, being of the type which includes an internal synchronization signal generator and an input/output terminal whereat an external synchronization signal can be received. The synchronization circuit further includes a comparator for receiving both synchronization signals and having a control output for supplying a terminal with the signal corresponding to the master/slave mode of operation of the synchronization circuit. A method of generating and supplying a synchronization signal to a plurality of electronic devices being operated as slave devices to a synchronization circuit acting as the master device is also provided.

Clock circuit and corresponding method for generating and supplying a

A switching power supply in which the oscillation frequency is dynamically controlled to have an instantaneous frequency value which is reduced when the power line waveform is near its peaks. This is preferably accomplished by a divider circuit, which provides an output current proportional to the ratio between the instantaneous value of the rectified voltage and the long-term-averaged value of that voltage. This output current is fed into a ramp generator, to dynamically shift the frequency of the ramp generator as the output current changes. This circuit is indifferent to power line voltage and frequency (over a fairly wide range), and therefore may be used in different countries having different power standards.

Frequency modulated, switching power supply

A circuit for regulating the charging time of the output node of an amplifier at start up. The output node commonly comprises an external soft-start capacitor charged by a current delivered by a pull-up transistor of a push-pull output stage of the amplifier, through a decoupling diode that is functionally connected between the output node of the amplifier and a terminal of the external soft-start capacitor. The present application provides a current mirror feed back circuit capable of mirroring the charge current of the external soft-start capacitor onto the driving node of the pull-up transistor of the output stage of the amplifier. The regulating circuit permits use of an external capacitance of extremely small size. Upon the reaching of a fully charged condition by the external capacitor, the control circuit self-isolates and does not influence in any way the normal operation of the amplifier.

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Fino Mornasco, Italy

Bruno Ferrario