Importance

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Abstract

Disclosed is an amplifier circuit with gain controlled by a current or a voltage. It is sought to obtain a linear gain as a function of the set value current or voltage, whereas amplifiers with controlled gain usually have a non-linear variation of the gain as a function of gain control voltage. According to the invention, there is proposed an amplifier circuit with the particular feature of having two identical amplifiers with controlled gain: one receives the signal to be amplified and gives an amplified output signal; the other receives a reference voltage or current and gives an output which is compared with a signal with a set value of variation in gain. The result of the comparison is used to automatically control the gain of the second amplifier to adjust its output to a desired value. The first amplifier receives the same automatic control signal as the second one. The second amplifier has its output automatically linked to a set value while, at the same time, having a fixed voltage or current as an input signal. It therefore has a known gain proportionate to the set value. Finally, the first amplifier, which is identical to the second one and receives the same gain control signal, thus has a gain proportionate to the set value, in accordance with what was desired.

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First Claim