Sgs-Thomson Microelectronics S.r.l.

Sgs Microelettronica Spa

Silvano Gornati

Maurizio Zuffada

Giorgio Betti

Fabrizio Sacchi

Silvano Coccetti

Roberto Viscardi

Gianfranco Vai

Mauro Merlo

David Macdara Moloney

Roberto Alini

Loic Lietar

A transconductor stage for high-frequency filters operated on a low voltage supply, being of a type which comprises an input circuit portion having signal inputs, further comprises a pair of interconnected differential cells (2,3) being associated each with a corresponding signal input. Each cell incorporates at least one pair of bipolar transistors (Q1,Q2;Q3,Q4) having at least one corresponding terminal thereof (e.g. the emitter terminal) connected in common.

Transconductor stage

A device for controlling the linearity of a horizontal deflection stage comprising a deflection yoke supplied with a yoke current controlled by a switch and series-connected to a capacitor for varying the yoke voltage according to the phase of the yoke current; the device comprising a circuit for detecting and generating a real signal proportional to the yoke current, a ramp generator for generating an ideal ramp signal having rising portions defining a given S-shaped wave:form, and an error amplifier for receiving the real and ideal ramp signals and generating an error signal for driving a power transistor having its emitter and collector terminals connected parallel to the capacitor for modifying the voltage in the capacitor so that the yoke current assumes the required waveform.

Horizontal deflection stage linearity control device

In a dynamic automatic loop for control of the overall gain of an input circuit of a superheterodyne receiver, the response time of the HF-AGC circuit of the TUNER, in response to the action of the TUNER DELAY circuit activated by the IF-AGC in the case of autonomously uncontrollable abrupt increases in the level of the antenna signal from the same HF-AGC of the TUNER, is markedly reduced using an additional TUNER DELAY PLUS circuit able to absorb for a determined interval of time, a discharge current from the storage capacitor the control voltage of the HF-AGC in addition to the discharge current absorbed by the existing TUNER DELAY circuit. The relevant intensity of this additional discharge current and its duration are optimized by way of suitable circuital arrangements in the design of said TUNER DELAY PLUS circuit. The response time is reduced without modifying the time constant of the HF-AGC, which cannot be freely reduced because of inter- and cross-modulation problems.

Control loop for reducing the time of repsonse of a tuner-AGC of a

A broad operational range, automatic device for the change of frequency in the horizontal deflection of multi-synchronization monitors comprises an integrated circuit incorporating,

Broad operational range, automatic device for the change of frequency in

A method of automatically measuring the horizontal scan frequency of a composite synchronism signal, comprising horizontal synchronization impulses at line frequency, consists of first performing a count of a number of impulses having a repeat frequency higher than said line frequency, as intervening between two successive impulses at line frequency. The count value, corresponding to said number of impulses, is stored to obtain the line frequency of the signal, and thereafter, a series of down counts is effected, as initiated at predetermined times, until a change of frequency of the signal is detected.

Method of automatically measuring the horizontal scan frequency of a

A method of demodulating multi-standard TV signals consists of providing a plurality of signals at a frequency which is a multiple of a reference frequency whose value is a common submultiple of the frequencies of the multi-standard signals. Thereafter, the signal to be demodulated is multiplied by one of said plural signals having a frequency which differs therefrom by a value equal to the reference frequency; by filtering the result of the multiplication, a signal is obtained at the reference frequency but corresponding in amplitude to the one to be demodulated.

Method of demodulating multi-standard TV signals and a circuit device

A temperature independent, dynamically compressed, DC control voltage is obtained by converting by means of a converter circuit employing a current mirror, a linear variation of the voltage across a control potentiometer, external to the integrated circuit, in a logarithmic differential voltage between two output voltage terminals, respectively on a first and a second branch of the converter circuit, the voltage signal taken from the first branch of the converter circuit being fed to the input of a unitary gain stage biased by a current generator with a temperature coefficient corresponding to the reciprocal of the temperature coefficient of integrated resistances and the corresponding output signal of the unitary gain stage being fed to a first input of a differential stage, to the second input of which is fed the signal taken from the second branch of the converter circuit. The differential stage being also biased by a current generator with a temperature coefficient equal to the reciprocal of the temperature coefficient of integrated resistances and having an integrated load resistance connected between the supply rail and the output terminal of the differential stage on which the desired temperature independent and dynamically compressed control voltage is produced. The circuit is particularly useful for generating a gain control current in an AGC system.

Integrated circuit for generating a temperature independent, dynamically

This variable-current source comprises a differential stage and a pair of voltage buffers which respectively receive, at the input, a variable input voltage and a reference voltage and are connected at the output to the differential stage. Both buffers comprise a resistor flown by a current which varies only as a function of the respective input voltage and of its resistance and therefore depends thermally exclusively on this resistance, and provide output voltages which depend upon these currents, so that the output current generated by the differential stage is temperature-independent.

Temperature-independent variable-current source

This high-precision oscillator stage, with reduced response times, includes only NPN transistors on the signal path and comprises a threshold detector circuit connected to a first and to a second threshold voltage and to the output of the stage so as to generate a differential voltage output signal which switches when each voltage threshold is reached, a control and memory circuit comprising a differential voltage detector connected to the output of the threshold detector and generating a charge and discharge signal depending on the state of the circuit, a memory element controlled by the differential voltage detector to maintain the charge and discharge states and an output driving circuit connected to the control and memory circuit so as to supply an external capacitor with constant currents so as to alternately and periodically charge and discharge the capacitor.

Current-controlled saw-tooth wave oscillator stage

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

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.

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Casorezzo, Italy

Silvano Gornati