Abstract: A multi-phase oscillator is provided. Said multi-phase oscillator includes a plurality of resonator stages series-connected in an ordered closed loop. Each stage is used for providing one or more oscillating voltages corresponding to an oscillating current. The oscillating current includes a natural current that is generated by the stage and one or more injected currents from a previous stage in the closed loop. The oscillating voltages provided by all the stages have substantially the same frequency; on the other hand, the oscillating voltages provided by each stage and the previous oscillating voltages provided by the previous stage have a corresponding phase difference. The oscillator further includes a coupler between each stage and the previous stage; the coupler is used for generating the injected currents according to the previous oscillating voltages.

Abstract: A multi-phase oscillator is provided. Said multi-phase oscillator includes a plurality of resonator stages series-connected in an ordered closed loop. Each stage is used for providing one or more oscillating voltages corresponding to an oscillating current. The oscillating current includes a natural current that is generated by the stage and one or more injected currents from a previous stage in the closed loop. The oscillating voltages provided by all the stages have substantially the same frequency; on the other hand, the oscillating voltages provided by each stage and the previous oscillating voltages provided by the previous stage have a corresponding phase difference. The oscillator further includes a coupler between each stage and the previous stage; the coupler is used for generating the injected currents according to the previous oscillating voltages.

Abstract: The invention relates to an elementary biquadratic cell for programmable time-continuous analog filters. The biquadratic cell is coupled between a first voltage reference and a second voltage reference and has at least one pair of input terminals and first and second pairs of output terminals. The cell includes a pair of half-cells, which half-cells are structurally identical with each other. Each half-cell comprises at least a first transistor coupled between the first and the second voltage reference and having a base terminal connected to a respective one of the input terminals. Each half-cell further comprises second and third transistors coupled between the first and second voltage references. The second transistor has a base terminal connected to the first output terminal of the first pair of output terminals and a collector terminal connected to the first output terminal of the second pair of output terminals.

Abstract: A control signal compensation method is particularly intended for an analog/digital processing system provided with a control loop, including in turn a controller and a monitoring circuit. The method includes storing corrections made by the controller, fast processing such as corrections before transmitting the corrections throughout the control loop, and generating a compensation signal for the latency effects of the controller, by the use of a negative feedback loop provided at the monitoring circuit level.

Abstract: An operational amplifier frequency self-compensated with respect to closed-loop gain comprises a transconductance input stage and an amplifier output stage connected serially together to receive an input signal on at least one input terminal of the amplifier and generate an amplified signal on an output terminal of the amplifier. Provided between the input and output stages is an intermediate node which is connected to a compensation block to receive a frequency-variable compensation signal therefrom. The compensation block is coupled with its input to the input terminal of the amplifier. The compensation block is connected to receive at least the feedback signal. Preferably, the compensation signal is variable as a function of a gain value which is determined by the feedback circuit, and said variation of the compensation signal occurs in a relationship of inverse proportionality to the gain value.

Abstract: An interface circuit is disposed between a generator of control signals and a plurality of electronic switches in order to produce boosted voltage signals corresponding to the control signals for activating the electronic switches. To avoid the use of a capacitor with a high capacitance and thus to reduce an area of the integrated circuit, the interface circuit includes a generator of activation signals and a plurality of voltage multipliers each having an input connected to an output of the control signal generator, an output connected to at least one terminal for activating an electronic switch and two control terminals connected to an activation signal generator. Each voltage multiplier includes MOS transistors operatively coupled in series between the input and the output. The MOS transistors operate in response to the activation signals to produce a boosted voltage on the capacitor.

Abstract: An operational amplifier frequency self-compensated with respect to closed-loop gain comprises a transconductance input stage and an amplifier output stage connected serially together to receive an input signal on at least one input terminal of the amplifier and generate an amplified signal on an output terminal of the amplifier. Provided between the input and output stages is an intermediate node which is connected to a compensation block to receive a frequency-variable compensation signal therefrom. The compensation block is coupled with its input to the input terminal of the amplifier The compensation block is connected to receive at least the feedback signal. Preferably, the compensation signal is variable as a function of a gain value which is determined by the feedback circuit, and said variation of the compensation signal occurs in a relationship of inverse proportionality to the gain value.

Abstract: An integrated operational amplifier with adjustable frequency compensation having a transconductance input stage and an amplifier output stage connected serially together between an input terminal and an output terminal of the operational amplifier. For the purpose of frequency compensation, moreover, a compensation block is connected across the input and the output of the output stage. The compensation block uses a plurality of charge storage elements connected in parallel together and in series with switch block which selects a sub-plurality of said charge storage elements in response to an external signal of the amplifier. The compensation block thereby provides an overall effective capacitance for frequency compensation.

Abstract: A high-pass filter includes at least one circuit unit constituted by a first branch and a second branch both connected to an input of the filter on one side and, on the other side, to an adder the output of which is the output of the filter. The first branch includes means for transferring an input signal substantially without modifying its frequency content, and the second branch comprises a low-pass filter. The circuit elements are chosen such that the components of the input signal with frequencies below the cut-off frequency of the low-pass filter are substantially cancelled out at the output of the adder. The filter is suitable for being produced within a particularly small area in an integrated circuit.

Abstract: A switching circuit utilizing MOS transistors without body effect having a first transistor inserted with source and drain terminals between two connection terminals, and a second and third transistors inserted in series by means of their respective source and drain terminals between the first transistor and a ground. The gate terminal of the second transistor is connected to the gate terminal of the first transistor to which is applied a command signal. Upon switching a signal is applied in phase opposition to the command signal to the gate terminal of the third transistor. The substrates of the first and the second transistors are connected to a connection node between the second and third transistors. The substrate of the third transistor is connected to ground.

Abstract: The speech circuit matches the impedance of the telephone line by synthesizing a complex impedance using a positive feedback loop which has a single resistor (11), and cancels out the side tone using a subtractor (20') which extracts from the signal (Va) coming from the line a signal (Vb) correlated to the signal to be transmitted. In order to achieve cancellation of the side tone unaffected by the noise produced in the impedance synthesizing circuits, the signal (Vb) is derived by processing the signal present in the resistor (11) at the output of the feedback loop.