Amplification factor monitor system null of amplification factor monitor circuit and gilbert die amplification factor variable amplifier of gilbert die amplification factor variable

摘要

PROBLEM TO BE SOLVED: To correctly monitor the amplification factor of a Gilbert-type amplification factor variable amplifier with simple configuration by providing an amplification factor monitor circuit, formonitoring the amplification factor of the Gilbert-type amplification factor variable amplifier. ;SOLUTION: The amplification factor monitoring circuit 100 for monitoring the amplification factor of the Gilbert-type amplification factor variable amplifier 4 includes a differential transistor pair to which a current is supplied from a constant- current source M12 and which respective control signals for controlling the amplification factor of the Gilbert-type amplification factor variable amplifier 4 are inputted. Moreover, a monitor output terminal 110 for outputting the current which is outputted from one transistor within the differential transistor pair is provided. Even with this kind of simple circuit configuration, a monitor current I is obtained with a monitor output terminal 110, and the amplification factor is correctly obtained. When the constant-current source M12 is constituted by resistance by which a constant voltage circuit and aresistance value are not easily changed, the current I₁₂ becomes stable with respect to the change of temp. and a power source voltage and the fluctuation of a process condition, so that the amplification factor is obtained more correctly.;COPYRIGHT: (C)1998,JPO