Sgs Microelettronica Spa

Sgs-Thomson Microelectronics Limited

Sgsates Componenti Elettronici S.p.a.

Silvano Coccetti

Roberto Viscardi

Silvano Gornati

Mauro Merlo

Pietro Erratico

Bruno Murari

Valerio Borghese

The circuit, particularly suitable for high-definition monitors, wherein a power amplifier is fed by a supply voltage source to generate a deflection current in a yoke, furthermore comprises switching means which are activatable to connect another source of a supply voltage higher than the source to the amplifier, and flyback detector means to activate said switching means at the beginning of the flyback.

Vertical deflection circuit for kinescope yokes, with flyback voltage

This circuit comprises a phase-lock stage receiving at the input a reference signal and the synchronism signal EN and generating at the output a triangular signal in phase correlation with the synchronism signal, a rectangular waveform generator receiving at the input the triangular signal and supplying at the output a rectangular signal, a drive element receiving the rectangular signal and generating a periodic control signal, as well as a phase comparator receiving at the input the triangular signal and the control signal, as well as a further reference signal and generating at the output an error signal correlated with the phase shift of the drive element and fed to the rectangular waveform generator. The reference signal fed to the phase-lock stage or to the phase comparator can be suitably varied within preset limits by an external potentiometer.

Phase regulation circuit, particularly for horizontal phase regulation

This circuit comprises a current source stage connectable to a capacitor which is controlled so as to alternately and periodically charge with the current fed by the source stage and discharge through a switch element, so as to generate a saw-tooth wave voltage. A buffer circuit, with low-impedance output is connected to the capacitor, for feeding a saw-tooth shaped low-impedance voltage signal to a load. In order to prevent the bias current of the buffer stage from introducing an error in the capacitor charge current and in the frequency of the saw-tooth voltage, a current sensor is provided connected between the buffer stage and the current source stage so as to vary the current generated by the source stage in an equal but opposite manner with respect to the error current due to the buffer stage.

Bias current compensating circuit, particularly for saw-tooth wave

This generator of periodic signals with exponential edges, which may be integrated at low cost, comprises a current source circuit connected to a capacitor and to a resistive element to supply them with currents having mutually correlated amplitudes, an amplifier interposed between the capacitor and the resistive element and adapted to maintain the voltage drop on the resistive element proportional to the voltage drop on the capacitor, and a switch device, connected in parallel to the capacitor and periodically switched off to allow the discharge of the capacitor.

Generator of periodial signals, in particular for switch-mode power

An amplifier stage with variable gain dependent on the anode voltage is interposed between a ramp generator having constant amplitude ramp output voltage and the vertical deflection stage in such a manner as to vary the input voltage of said vertical deflection stage in accordance with anode voltage variations. In such a manner the vertical deflection current varies correspondingly.

Control circuit with compensation of the anode voltage variation for

A variable-gain rectifier-amplifier with regulated voltage converts the output ramp of a ramp generator with regulating resistance of ramp amplitude into a triangular wave form with adjustable linearity which a feedback circuit brings back to said regulating resistance in the form of alternating current superimposing it on the direct current regulated through said resistance. This provides an S correction of the output ramp which depends on the gain regulation voltage of the rectifier-amplifier circuit.

Electric circuit for S correction of the vertical scanning ramp in a

This high accuracy, RC oscillator, particularly for monitors, has different switch-over thresholds independent from such variable parameters as the saturating voltage of transistors, and has a high operating frequency. The oscillator comprises a capacitor having an output terminal, a capacitor power current source, and a control section. The control section is composed of a plurality of differential stages sharing a common input and each having an input connected to a different switch-over threshold. The control section further comprises a switch-over drive stage connected to the oscillator output terminal and to an input terminal thereof for controlling activation and deactivation of the different differential stages (and hence, of the respective associated thresholds) according to the signal present at the output and input terminals of the oscillator.

RC oscillator having plural differential threshold stages

A protective current mirror, with a reflection ratio greater than one, is connected as the active load of an input differential amplifier of a power amplifier. This mirror is provided in addition to the usual current mirror which has its output connected to the drive transistor of the output power amplifier stage. The protective mirror senses the imbalance due to a voltage peak which occurs at an inverted input of the input differential amplifier at the very beginning of the descending portion of a sawtooth input signal ramp voltage and the protective mirror operates a protective transistor which is connected to the base of the power amplifier drive transistor so as to keep one power transistor of the final power amplifier stage in its inactive state. Protection of the output power transistor occurs before the output of the power amplifier has reached its maximum voltage level.

Power amplifier protection circuit

A voltage divider with at least two intermediate taps of almost the same potential is formed in an integrated-circuit chip by diffusing P-type impurities into an N-type substrate along a narrow strip zone ending in enlarged terminal areas. The strip zone has at least two narrower transverse branches which form closely adjoining junctions with it and extend laterally in the same or in opposite directions. Upon application of a voltage difference across the strip zone by means of electrodes placed on the two terminal areas, output terminals in contact with the free ends of the branches remote from the strip zone and connected to high-resistance loads carry potentials substantially equal to those of the corresponding junctions.

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Vittuone, Italy

Silvano Coccetti