Abstract: In a device that includes a pair of closed-loop voltage regulators each including an input transconductance stage receiving a reference voltage and a feedback voltage, an intermediate transresistance stage, an output buffer operatively in cascade for generating on an output node the regulated output voltage and negative feedback means for providing the feedback voltage to the input stage, the method includes a circuit that limits the difference between two output regulated voltages. The limiting circuit includes a differential transconductance amplifier input with voltages proportional to the output voltages of the regulators or obtained by adding an offset voltage to the output voltage of the regulators for injecting in, or draining from, an input node of the intermediate stage of one of the regulators, a current as a function of the relative unbalance of the differential transconductance amplifier.

Abstract: An amplifier having an input; an output supplying an output signal, and a feedback network connected between the input and the output, and a distortion detection circuit. The feedback network includes a first and a second feedback element arranged in series and forming an intermediate node supplying an intermediate signal in phase with the output signal in absence of distortion, and in phase-opposition with the output signal in presence of distortion. The distortion detection circuit includes a phase-comparating circuit which detects the phase of the output signal and of the intermediate signal, and generates a distortion-indicative signal, when the intermediate signal is in phase opposition with respect to the output signal.

Abstract: An amplifier having an input; an output supplying an output signal, and a feedback network connected between the input and the output, and a distortion detection circuit. The feedback network includes a first and a second feedback element arranged in series and forming an intermediate node supplying an intermediate signal in phase with the output signal in absence of distortion, and in phase-opposition with the output signal in presence of distortion. The distortion detection circuit includes a phase-comparating circuit which detects the phase of the output signal and of the intermediate signal, and generates a distortion-indicative signal, when the intermediate signal is in phase opposition with respect to the output signal.

Abstract: A current generator circuit with controllable frequency response has at least one current mirror formed of MOS transistors, being powered through a terminal held at a constant voltage, having an input leg through which a reference current (I1) is driven by a first current generator (G1), and having an output leg for generating, on an output terminal (OUT) of the mirror, a mirrored current (I.sub.out) which is proportional to the reference current (I1). The input leg includes at least a first transistor (M1) which is diode-connected and has a control terminal (Ga1) coupled to a corresponding terminal (Ga2) of a second transistor (M2) included in the output leg. In accordance with the invention, the mirror circuit also has an impedance matching circuit connected across the control terminals (Ga1 and Ga2) of the first and second transistors and configured to hold the same voltage value at both terminals (Ga1 and Ga2).

Abstract: A current generator circuit with controllable frequency response has at least one current mirror formed of MOS transistors, being powered through a terminal held at a constant voltage, having an input leg through which a reference current (I1) is driven by a first current generator (G1), and having an output leg for generating, on an output terminal (OUT) of the mirror, a mirrored current (I.sub.out) which is proportional to the reference current (I1). The input leg includes at least a first transistor (M1) which is diode-connected and has a control terminal (Ga1) coupled to a corresponding terminal (Ga2) of a second transistor (M2) included in the output leg by an impedance matching circuit configured to hold the same voltage value at both terminals (Ga1 and Ga2). The impedance matching circuit has an adjustable output impedance, specifically lower in value than the value to be had without this circuit. It functions to regulate the impedance on the control node (Ga2) of the second transistor (M2).

Abstract: A circuit comprising a transistor which, when supply is turned off, locks the output of the audio amplifier to the supply line, the potential of which is reduced gradually by a filter capacitor, so that the output voltage follows the supply voltage with the same slope, and is so controlled by the filter capacitor, thus eliminating undesired noise ("popping") at the output caused by electric transients in the audio amplifier.

Abstract: A circuit comprising a transistor which, when supply is turned off, locks the output of the audio amplifier to the supply line, the potential of which is reduced gradually by a filter capacitor, so that the output voltage follows the supply voltage with the same slope, and is so controlled by the filter capacitor, thus eliminating undesired noise ("popping") at the output caused by electric transients in the audio amplifier.

Abstract: A circuit for controlling on-off switching of an audio amplifier in such a manner as to prevent sharp uncontrolled variations of the output during switching from resulting in undesired noise (popping) on the loudspeakers. For so doing, the circuit provides for generating a controlled positive potential at the negative input in relation to the positive input of the amplifier when this is switched on or off. More specifically, when switching on, the potential difference is maintained pending switching of all the sources on the amplifier, after which, it is gradually eliminated for enabling the output to reach the steady-state value slowly and in controlled manner; whereas, when switching off, the potential difference is generated gradually for enabling the output of the amplifier to be grounded slowly prior to turning off the amplifier itself.

Abstract: A circuit for sensing the output distortion of amplifier stages of the type which has a first input which receives a voltage signal to be amplified, a second input connected to a feedback network and an output which generates an amplified output signal. The circuit comprises at least one comparator, which receives in input a first signal which is correlated to the voltage signal and a second signal which is correlated to the output signal of the amplifier stage, and is enabled so as to generate a distortion signal in output when the second signal exceeds the first one in terms of absolute value, i.e. in the presence of distortion.