Stmicroelectronics S.a.

Stmicroelectronics Gmbh

Didier Salle

G&eacute;rard Bret

Gerard Bret

A device for regulating the amplitude of a chrominance signal includes a variable gain amplifier having an input receiving a sub-carrier signal, and an output providing a regulated sub-carrier signal. The gain of the amplifier is controlled by two regulation loops. The first regulation loop operates during the duration of the reference burst. The second regulation loop operates during the visible line. Each of these loops include an up/down counter controlled by a clock. A digital-analog converter has an input receiving the output signals from the first and second up/down counters. An output signal from the digital-analog converter is connected to the gain control of the amplifier. The digital-analog amplifier is controlled by another clock.

Chrominance signal amplitude regulation device

The demodulating device for a chrominance signal includes an oscillator with a controlled frequency, and an adjuster for adjusting the oscillator frequency as a function of a charge voltage of a memory capacitor. The adjuster preferably includes a fine adjustment channel to output a first adjustment value that depends on the charge voltage of the memory capacitor, and a coarse adjustment channel to output a second adjustment value. The second adjustment value is modified when the charge voltage of the memory capacitor is not within a given range. The device is used, for example, in integrated SECAM decoders.

Demodulator, particularly for a SECAM chrominance signal, with double frequency adjustment

The SECAM chrominance signal demodulator includes an oscillator with a controlled frequency, a phase comparator with a first input connected to an oscillator output, a second input to receive a chrominance signal, and an output connected to an input loop of the oscillator. The demodulator further includes a fixed current source, also connected to the loop input, a current mirror to copy a current equal to the sum of the fixed current and a comparator output current in the output branches comprising first and second calibration resistors respectively, in series with a common resistor. Output voltages corresponding to the red and blue components of the chrominance signal are measured at the terminals of the calibration resistors respectively. The demodulator is used in television sets, for example.

Secam chrominance signal demodulator with two red-blue channels and a

A current-controlled oscillator includes a capacitor, and at least one current source for providing at least one charge current for charging the capacitor. A discharge circuit sequentially discharges the capacitor with a discharge current. A control circuit maintains a mean charge voltage of the capacitor at a preset value by controlling the discharge current. The control circuit includes a current control source forming a current mirror with the at least one current source. The current control source is connected to the discharge circuit for setting the discharge current substantially equal to a sum of the charge currents. The oscillator further includes a correction circuit for correcting the discharge current corresponding to a mean charge of the capacitor.

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Grenoble, France

Didier Salle