Abstract: A method and an equalizer circuit equalize signals transmitted on a line having an attenuation. The equalizer circuit includes: an analogical adaptive filter applied in series with the line and includes plural transconductance filters each having a bias current. The adaptive filter has a pole and a zero each having a frequency position in the working band that is variable in response to the bias current. The equalizer circuit includes a retroaction circuit applied to the output of the filter and able to vary the bias current according to the varying of the attenuation of the line. The bias current of the transconductance filters has a prefixed value and is made to vary at the increasing of the attenuation so that the pole is moved toward high frequencies and the zero is moved toward low frequencies.

Abstract: The invention relates to a monolithically integrated telephone circuit for driving wide-band telephone lines and transmitting digital data at a very high frequency. The telephone circuit is powered from a battery DC supply providing a pair of voltage references. The telephone circuit includes an output circuit portion including a pair of differential output stages, each having a pair of inputs and being connected with its output to a respective lead of a two-wire telephone line. The telephone circuit also includes a device for deriving a reference voltage from the supply voltage, and includes a low-voltage supply network which is input a DC signal and produces a voltage reference to be added to the reference voltage for delivery to one input of each output stage. The other input of each stage receives an AC signal in order to present at the circuit output a suitable AC+DC differential voltage for driving the telephone line.

Abstract: A method and an equalizer circuit equalize signals transmitted on a line having an attenuation. The equalizer circuit includes: an analogical adaptive filter applied in series with the line and includes plural transconductance filters having a bias current each and to which it is associated a pole and a zero the position in frequency of which in the working band is variable in response to the bias current; a retroaction circuit applied to the output of the filter able to vary the bias current; the bias current varying at the varying of said attenuation of said line; wherein the bias current of the transconductance filters has a prefixed value; the bias current is made to vary at the increasing of the attenuation so that the pole is moved toward high frequencies; and the bias current is made to vary at the increasing of the attenuation so that the zero is moved toward low frequencies.

Abstract: A comparator circuit includes a differential input stage, a second differential stage having a differential output, and an output stage transforming an output signal from the differential output of the second differential stage into an output signal having a logic level. The comparator further includes a common mode measuring stage. The common mode measuring stage includes a differential pair of input transistors and a differential pair of complementary transistors biased by respective current generators, and a current mirror summing the differential output currents of the two complementary transistors pairs into a single output current signal. A switching stage is controlled by the differential output nodes of the second differential stage. A common source node of the switch stage is coupled to the output of the common mode measuring stage and to the differential output nodes of the differential input stage.

Abstract: The present invention relates to a control signal generation circuit for telephone charge indicators comprising a capacitor having a first and a second terminals connected to ground through respectively a first and a second switches with the first terminal of the capacitor being also connected through a third switch to a constant current generator which is connected to a positive power supply line with respect to ground. The second terminal of the capacitor is connected to a constant current generator which is connected to a negative power supply line with respect to ground. The first and second terminals are also connected through respectively a first and a second resistance to a circuit node coupled to an output terminal.