Circuit arrangement for adjusting the amplitude of a signal

摘要

A circuit arrangement for adjusting the amplitude of a signal includes first and second differential transistor-amplifiers. One of said amplifiers is arranged to receive the signal via its main-current-path input and the other amplifier is arranged to receive a direct current supply corresponding to the d.c. component of the signal. The amplitude of the signal is adjustable by means of a control voltage applied to the cross-coupled control terminals of the differential amplifiers, and the amplitude adjusted signal is available on two cross-coupled main-current path outputs of the amplifier. The circuit can be energized with low supply voltages and at the same time can handle large amplitudes of the signal to be adjusted by means of a current summing circuit in which an output direct current corresponding to the direct current supplied is subtracted from the amplitude adjusted signal. Current mirror circuits apply the signal, the direct current supply and the output direct current to the first and second differential amplifiers and the current summing circuit resepctively. Voltage sources are provided from which the signal, the supply direct current and the output direct current can be derived.