Abstract: The common terminals of the two opposite transistors of a differential stage with an input signal represented by the voltage applied between the bases of the two transistors are connected to ground through two further transistors controlled by the current which passes through the above-mentioned transistors. The output signal is represented by the current which passes through one of said further transistors.

Abstract: A telephone circuit which may be monolithically integrated, for generating control signals for displaying the telephone charges to a telephone user, is coupled to a AC voltage signal generator having a predetermined amplitude and frequency which are constant over time. The circuit includes a voltage generator for generating voltage signals which are spaced over time and have a trapezoidal pulse waveshape. A multiplier circuit calculates the product of the signals supplied by the two generators and supplies a signal which is sent to the speech circuit of the subscriber's line and is added to the speech (i.e.--conversation) signals. The circuit also includes a circuit for receiving an image signal of the overall signal adapted to the telephone line; a high-pass filter for eliminating the speech signal components from the image signal; a rectifier circuit for rectifying the filtered signal and a comparator for comparing the rectified signal with a reference signal.

Abstract: A transistorized bridge rectifier circuit with overcurrent protection which can be integrated monolithically is used for joining to a two-wire telephone line to the electronic circuits of a telephone subscriber set connected thereto. The circuit includes a transistorized bridge having a circuit arranged in the manner of a Graetz bridge. Rather than using separate elements for overcurrent protection, the circuit uses the bridge circuit elements themselves as protection elements. Diodes or diode connected transistors are respectively connected between the base and collector of transistors in two arms of the Graetz bridge and the resultant circuit thus provides overcurrent protection without the need of additional protection elements.

Abstract: A final bridge stage for a receiver audio amplifier, which can be monolithically integrated, consists of two pairs of complementary bipolar transistors. The collectors of the transistors of each of the transistor pairs are connected together to form two terminals to which a transducer is connected. The transistor emitters of NPN type and PNP type transistors are respectively connected to the negative pole and, through a constant current generator, to the positive pole of a supply voltage generator. The constant current generator consists of a small resistor to which a constant voltage is applied by means of a suitable circuit. The bases of the bridge transistors are connected to the signal source by means of suitable circuits. The signal source controls similar transistors in phase opposition, while at the same time controlling the complementary transistors in phase opposition.

Abstract: A transistor bridge rectifier circuit, which is capable of being monolithically integrated, is designed to connect the electronic circuits in a user's telephone set to a two-wire telephone line. The circuit includes a transistor bridge with a "Graetz bridge" circuit arrangement, a current generator, a pair of current mirror circuits connected thereto, which alternately conduct according to the polarity of the line, and a pair of controlled current gain transistors, each controlled by the output of one of the two current mirror circuits. The transistors belonging to the opposite sides of the bridge, the bases of which are respectively connected to the emitter and collector of the same controlled current gain transistor, are biased with the same base current which flows through the controlled current gain transistor.

Abstract: A linear differential amplifier comprises two main transistors of one conductivity type (e.g. PNP) having emitters connected via a common constant-current generator to an ungrounded terminal of a d-c supply whose grounded other terminal is connected to their collectors via a pair of identical resistors; the base of one of these transistors is grounded while the base of the other transistor receives an a-c input signal. An unbalanced output signal is taken off the collector of an ancillary transistor of the opposite conductivity type (NPN) which is fed from the ungrounded supply terminal through a complementary auxiliary transistor or through another constant-current generator; the emitter of this output transistor is connected directly to the collector of the second main transistor.

Abstract: Two cascaded capacitors, one in series and the other in shunt with a load, are connected across a source of amplitude-modulated oscillations with interposition of a small resistance, preferably the forward resistance of a series diode. The junction (A) of that resistance with the series capacitor is connected to the emitter of a transistor whose collector is energized with a high driving voltage (positive in the case of an NPN transistor) and whose base is tied to a tap on a voltage divider inserted between that collector and the opposite, usually grounded source terminal. The section of the voltage divider between the base and ground may consist of the forward resistance of a single diode, designed to balance the base/emitter threshold of the transistor whereby the aforementioned junction (A) is at ground potential when the source voltage peaks with a polarity opposite that of the collector potential.