RILEVAZIONE E CONTROLLO DI MODO COMUNE IN CATENA DI AMPLIFICICATORI BILANCIATI

In a chain of fully differential amplifiers, comprising at least two cascaded amplifiers, the stabilization of the output common mode voltage of an amplifier is implemented by sensing the value of such a voltage by means of a dedicated terminal connected to a circuit node corresponding to the sources connected in common of the input differential pair of transistors of an amplifier which follows in the chain of cascaded amplifiers. Such a voltage is compared with a reference voltage to which, by means of a level shifting circuit, a voltage equivalent to the threshold voltage of the said transistors forming said input pair is subtracted thus obtaining an error signal of the output common voltage of said amplifier to be stabilized which may be applied to a dedicated control terminal thereof. The system of the invention provides for the sensing of the output common mode voltage without loading the ouputs of the amplifier to be stabilized and it is more easily implemented than known systems.