Thomson Broadcast Systems

Claude Claverie

Patrick Hardy

Stephane Hergault

Daniel Boisseau

Xavier Guitton

An amplification circuit comprising a device for compensating for its input current. The amplification circuit includes an amplifier and a capacitor located on the input side of the amplifier. The input-current compensation device consists of a current generator, generating a current Ig, a switch and a device for measuring the average current charging or discharging the capacitor during the time that the switch is open. The current Ig is such that: Average current=Ia-Ig, where Ia is the input current of the amplifier. The value of the average current is close to zero. The value of the current Ig which the current generator must output, so as to make the average current close to zero, is calculated using the device for measuring the average current. The invention particularly applies to a circuit for restoring the DC component of a video signal.

Amplification circuit which includes an input-current compensation device

Frequency modulated signals are demodulated through a limiter circuit that chops the signal to give pulses whose occurrence frequency is proportional to the instant frequency of the received signal. The invention is devoted to a new processing of those pulses. The leading edges of the pulses are time integrated. The obtained signal is then as usual, low pass filtered to give the demodulated signal. The main advantage of this new processing is that the circuit that makes this processing does not implement delay lines and can then be made as a single chips.

Monolithically integrable frequency demodulator device

In a detector for detecting a frequency-modulated light wave including a PIN photodiode (2), biasing means (11, 12, 15) are introduced which are capable of automatically forward biasing or reverse biasing the PIN photodiode (2) depending on the received light power. The output voltage of a transimpedance preamplifier stage (6) receiving the signal from the PIN photodiode (2) is thus automatically limited to a value below the saturation threshold of this transimpedance preamplifier stage (6).

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Rennes, France

Claude Claverie