Stmicroelectronics S.a.

Sgs-thomson Microelectronics S.a.

Gerard Bret

Pascal Debaty

Michel Imbert

Didier Salle

A bandpass filter includes a first and a second transconductor. The first transconductor has a first input connected to ground, and a second input connected to a second input of the second transconductor and to the output of the filter. An output of the first transconductor is connected to a first input of the second transconductor, and to an input of a filter through a first capactor. The output of the second transconductor is connected to ground through a second capacitor, and to a monitor amplifier. An output of the monitor amplifier is connected to the output of the filter. The bandpass filter further includes a third capacitor arranged between the second input and the output of the first transconductor, and a splitter bridge connected to the second input of the second transconductor.

Bandpass filter with transconductors

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 circuit with a voltage-controlled variable resistance comprises a MOS transistor (2), one of the main electrodes (S) of which is connected to a common terminal (B), a control voltage (VC) being applied between its control electrode (G) and the common terminal. This circuit comprises a voltage dividing bridge (R1, R2) switched between a first terminal (A) and a common terminal (B) and a follower (6, 4), the input of which receives the output (5) of the divider (R1, R2) and the output (8) is connected to the other main electrode (D) of the MOS transistor; whereby the resistance between the first terminal (A) and the common terminal (B) varies as a function of the control voltage (VC).

Circuit with a voltage-controlled resistance

A SECAM decoder comprises an input receiving a chrominance subcarrier (SP); first and second outputs delivering respectively the decoded blue (B2) and red (R2) signals; a first PLL phase demodulator (30) receiving the subcarrier (SP), operative only during the blue lines; a second PLL phase demodulator (31) receiving the subcarrier, operative only during the red lines; a first adder (32) receiving the output signal (B1) of the first demodulator (30) and this same signal delayed by a line period to deliver the decoded blue signal (B2); an adder (33) receiving the output signal (R1) of the second demodulator (31) and this same signal delayed by a line period to deliver the red decoded signal (R2).

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Echirolles, France

Gerard Bret