Abstract: A telephone comprises an acoustic alarm, conversation members, first control means for the acoustic alarm, second control means for the conversation members, first supply means and second supply means for absorbing energy from a telephone line, the first supply means and the second supply means supplying the first control means in a call condition and the second control means in a conversation condition, respectively, wherein the first supply means further supplying the second control means in the call condition.

Abstract: An analog input circuit may include a pair of differential transconductance input stages having input nodes connected in parallel and which are fed the analog input signal. One of the differential transconductance stages may have common mode compatibility toward the supply node at the highest potential, and the other stage may have common mode compatibility toward the supply node at the lowest potential. Furthermore, differential output currents of the transconductance input stages may be summed differentially on first and second input nodes of a differential converter stage, which converts the differential current signals to an amplified differential voltage output signal.

Abstract: An analog input circuit may include a pair of differential transconductance input stages having input nodes connected in parallel and which are fed the analog input signal. One of the differential transconductance stages may have common mode compatibility toward the supply node at the highest potential, and the other stage may have common mode compatibility toward the supply node at the lowest potential. Furthermore, differential output currents of the transconductance input stages may be summed differentially on first and second input nodes of a differential converter stage, which converts the differential current signals to an amplified differential voltage output signal.

Abstract: A buffer having a circuit for reducing the slope of an input signal and a negative feedback circuit that generates a regulating signal dependent on the variation of the output signal and that applies the regulating signal to the input of the buffer. A precise regulation of the slope, independent of variations in the production process and of environmental conditions, is achieved.

Abstract: An operational amplifier includes a first stage, and a second stage with an input connected to an output of the first stage and an output connected to a load. The second stage includes between its input and its output a first signal path for driving the load in a first direction, and a second signal path for driving the load in the opposite direction. The first and second signal paths have substantially equal gains for small signals, substantially equal output impedances for small and large signals, and substantially equal output-current capabilities.

Abstract: A telephone comprises an acoustic alarm, conversation members, first control means for the acoustic alarm, second control means for the conversation members, first supply means and second supply means for absorbing energy from a telephone line, the first supply means and the second supply means supplying the first control means in a call condition and the second control means in a conversation condition, respectively, wherein the first supply means further supplying the second control means in the call condition.

Abstract: An operational amplifier includes a first stage, and a second stage with an input connected to an output of the first stage and an output connected to a load. The second stage includes between its input and its output a first signal path for driving the load in a first direction, and a second signal path for driving the load in the opposite direction. The first and second signal paths have substantially equal gains for small signals, substantially equal output impedances for small and large signals, and substantially equal output-current capabilities.

Abstract: A fully differential amplifier, in other words one having differential inputs and outputs, is associated with a circuit to regulate the output voltage reference. This circuit contains a resistive divider connected between the output terminals of the differential amplifier, a diode between the intermediate connection of the divider and common bases of load transistors of the differential amplifier, and a current mirror having a first branch connected to a reference voltage generator and a second branch which forms a current generator connected between the common bases of the load transistors and ground. This provides an efficient feedback control system with low power consumption and takes up less space on an integrated circuit.

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.