Abstract: A self-configurable, dual bridge, power amplifier has a window comparator sensing the level of input signals fed to the amplifier which-drives a plurality of configuring switches capable of configuring the amplifier as a single bridge amplifier driving a first and a second loads connected in series or as two distinct bridge amplifiers each driving one of the two loads. As long as the two levels of the input signals remain comprised between a range defined by a negative voltage reference and a positive voltage reference, the amplifier is configured as a single bridge driving the two loads in series, thus reducing sensibly power dissipation. Several embodiments of the configuring means are shown.

Abstract: An AB class stage is described which comprises two complementary MOSFET final transistors connected in a push-pull manner between two supply terminals. In order to attain high linearity, low switching distortion, a high ratio between the maximum output current and the rest current, independence of the rest current from the temperature and manufacturing variables and a circuit simplicity, the circuits determining the rest current and those which provide current to the load are substantially independent of one another. More particularly, two transconductance amplifiers are provided which control the final transistors and are dimensioned so as to have zero output current in rest conditions, two voltage generators which determine the rest current and two resistors being connected between the gate electrodes of the final transistors and the supply terminals.

Abstract: A circuit assembly for an operational amplifier has an input stage with first and second input terminals and an output terminal. An output stage has a first input terminal coupled to the output terminal of the input stage, a second input terminal, and an output terminal. A feedback circuit is coupled between the output terminal of the output stage and the second input terminal of the input stage. An interconnection circuit is coupled to the first and second input terminals and the output terminal of the output stage and to a reference voltage source. The interconnection circuit has first, second, and third modes, such that the second input terminal of the output stage is coupled to the reference voltage source when the interconnection circuit is in the first mode.

Abstract: A circuit for dividing a reference current is composed of a number n of transistors connected in cascade, in a Darlington configuration, between current generator and a fractionary current output node and by N+k (where k is an integer different from zero) directly biased diodes in series, connected between the generator and the fractionary current output node. The circuit does not employ current mirrors, so all transistors may have the minimum size, which also minimizes the effects of leakage currents. Additionally, compensation elements may be used for compensating the leakage currents from the base regions of the transistors. The circuit is useful as a capacitance multiplier, or as a slow ramp generator in a large number of design situations. Independence from intrinsic parameters of the transistors used and/or from temperature of operation may be provided by employing a specifically designed reference current generator. Several embodiments are described.

Abstract: A turn-on control circuit having a comparator supplied with a turn-on voltage increasing gradually during the turn-on phase of a device for protection. When the control voltage reaches a predetermined value, the comparator supplies a diagnostic enabling signal to a diagnostic stage, which, in the event an undesired condition is detected at an output of the device, supplies a clamp enabling signal to the control terminal of a clamping transistor located between the input of the circuit and ground, and which, when enabled, prevents the turn-on voltage from increasing further, and so prevents the device from being turned on.

Abstract: A transistor in an output stage has an emitter connected to a supply rail and a collector connected to an output node. The transistor is protected against the effects of accidental shortcircuiting of the output node of the output stage with a positive pole of a battery while the circuit is unpowered, by a protection transistor of the same type as the transistor to be protected. The protection transistor has an emitter connected to the base of the output transistor, a collector connected to the output node of the output stage, and a base connected through a biasing resistance to the supply rail on the output stage. The protection transistor and an interdigitated structure of the transistor may be formed within the same pocket, thus reducing the required area.

Abstract: A self-configurable, dual bridge, power amplifier has a window comparator to sense amplifier signals and control a plurality of configuring switches capable of configuring the amplifier either as a single bridge amplifier driving two loads connected in series or as two distinct bridge amplifiers each driving one of the two loads. When the two amplifier signals remain within a range defined by a negative voltage reference and a positive voltage reference, the amplifier is configured as a single bridge driving the two loads in series, thus reducing power dissipation. Several embodiments of the invention are shown.

Abstract: A device including a MOS power transistor, and a temperature sensor including a bipolar transistor integrated in the MOS transistor and having its emitter and collector connected directly to the source and gate terminals respectively of the MOS transistor. Parallel to the base-emitter junction of the bipolar transistor, there is connected a voltage source for biasing the junction to such a value that the bipolar transistor remains off at room temperature, and absorbs the maximum current supplied by a drive circuit of the MOS transistor at the maximum permissible temperature TUM. At temperature TUM, the bipolar transistor takes over control of the gate-source voltage of the MOS transistor for maintaining thermal feedback of the device at maximum temperature TUM.

Abstract: A self-configurable, dual bridge, power amplifier has a window comparator sensing the level of input signals fed to the amplifier which drives a plurality of configuring switches capable of configuring the amplifier as a single bridge amplifier driving a first and a second loads connected in series or as two distinct bridge amplifiers each driving one of the two loads. As long as the two levels of the input signals remain comprised between a range defined by a negative voltage reference and a positive voltage reference, the amplifier is configured as a single bridge driving the two loads in series, thus reducing sensibly power dissipation.

Abstract: An amplifier comprising a power stage the output of which is compared with a reference level by a comparator. If the output exceeds the reference level, a reduction is made in the gain of a variable-gain cell upstream from the power stage. The reference level varies with temperature, and, more specifically, presents a high constant value (e.g., greater than the supply voltage) when temperature is below a predetermined threshold (e.g., 130.degree. C.), and decreases in proportion to an increase in temperature, when the temperature exceeds the predetermined threshold. Thus, the input signal is only attenuated in the event the output signal exceeds given values inversely proportional to temperature, and with no reduction in peak output at high temperature.

Abstract: Unitary-gain final stage particularly for monolithically integratable power amplifiers, which comprises a pair of final N-channel MOS power transistors. The first transistor has its drain terminal connected to a supply voltage and its source terminal connected to the drain terminal of the second transistor. The source terminal of the second transistor is connected to the ground. The output terminal of the power amplifier is connected between the source terminal of the first transistor and the drain terminal of the second transistor. The final stage furthermore comprises a high-gain feedback differential amplifier which has its non-inverting input terminal connected to the input of the power amplifier, its inverting input terminal connected to the output terminal of the differential amplifier and its output terminal connected to the gate terminal of the second transistor. A leveling circuit is furthermore connected to the gate terminal of the second transistor.

Abstract: Voltage/current characteristics control circuit particularly for protecting power transistors, which comprises at least one power transistor; the emitter terminal of a first transistor is directly connected to the output of the power transistor; the emitter terminal of a second transistor is connected to the first terminal of the power transistor by means of a first resistor. The collector terminal and the base terminal of the first transistor are connected to a current source. The base terminal of the first transistor is connected to the base terminal of the second transistor, and the circuit furthermore comprises a protection circuitry. The circuitry is connected to the collector terminal of the second transistor through a differential stage which comprises a third transistor and a fourth transistor; the third transistor and fourth transistor have a respective second resistor and third resistor arranged in series.

Abstract: The amplifier comprises a first and a second amplifier block of opposite phase driven by a single input signal and having its outputs connected to the two terminals of a load. It also comprises circuit means to disable one of the said amplifier blocks when the absolute value of the input signal is less than a predetermined threshold level. A passive feedback system capable of maintaining the amplifier gain constant is located between the aforesaid terminals of the load and the inputs to the two amplifier blocks.

Abstract: A circuit for limiting temperature without distortion in audio power amplifiers, comprising a temperature sensor for sensing the temperature in an audio power amplifier, and a variable-gain amplifier connected ahead of the audio power amplifier circuit and having a gain control input connected to the temperature sensor to vary the input signal of the audio amplifier in a linear manner. A linear limitation of the power, and therefore of the temperature, is thus obtained in the audio amplifier without introducing distortion.

Abstract: An integratable power transistor with optimization of direct secondary breakdown phenomena which comprises a plurality of elementary transistors which are arranged side by side and comprise a plurality of cells, each of which is formed by an emitter reigon surrounded by base and collector regions, with the emitter regions arranged physically separated. According to the invention, the base regions are also arranged physically separated and are mutually connected by resistive elements.

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.

Abstract: A muting circuit for audio amplifiers having first and second input stages, being supplied a supply voltage via a source, with respective outputs connected in parallel with each other to the input of an output stage and having a signal input applied to the second stage, comprises means of switching over the power supply between the first and the second stages operatively linked to the comparator means effective to compare the values of a reference voltage, associated with the pattern of the supply voltage with a predetermined time delay, to respective predetermined voltage values below the supply voltage.

Abstract: In an integrated amplifier comprising at least a pair of operational amplifiers which may be connected in a single-ended configuration to form a stereo amplifier or alternatively in a bridge configuration to increase the output dynamics, a single constant current generator for generating a current having a value which is twice the value of the bias current of the input stages of the two operational amplifiers, is connected between an inverting input of one of the two operational amplifiers and ground, and allows for elimination of the offset voltage without contributing to an increase, in any appreciable way, of the noise level at the inputs and without the signal applied to the input terminals of the integrated amplifier causing modulation problems.

Abstract: A so-called bridge audio amplifier, particularly for stereophonic car radio sets, comprises a first power amplifier in a non-inverting configuration which is connected to a second amplifier in an inverting configuration. This audio amplifier further comprises a first resistor pair forming a bridge circuit with the resistors of the first power amplifier, as well as a second resistor pair interconnected between a positive supply pole and ground and with the first and second amplifiers having their respective non-inverting inputs connected across the second resistor pair via respective input resistors. The audio amplifier of this invention requires but a very small number of input pins and may be used as a stereophonic amplifier.

Abstract: This low voltage-controlled, stand-by electronic circuit with delayed switch off, comprises a switching circuit defining a stand-by input receiving a stand-by switching signal and an output, and a delay circuit generating a delayed switch off signal. The switching circuit comprises a controlled current source having two control inputs, one whereof is connected to the stand-by input for switching on the controlled current source upon receiving the stand-by switching signal and the other of the inputs is connected to the delay circuit. The delay circuit is also connected to the stand-by input and receives therefrom the stand-by switching signal for generating the delayed switch off signal, so that the controlled current source is switched on upon receiving the stand-by switching signal and remains on in absence of the stand-by switching signal and of the delayed switch off signal, the controlled current source being switched off by the delayed switch off signal on the second control input.