Patent ID: 6717469
Filing Date: 2004-04-06
Classification: H03F,H03G

Abstract:
A gain control circuit, in which a gain in a variable gain cell is controlled according to a gain control current of a value K1Â·Vcont (K1 denotes a proportional constant) corresponding to a gain control voltage Vcont, a gain reference current of a value K3 corresponding to a reference voltage and a bias current of a value K2Â·T (K2 denotes a proportional constant, and T denotes an absolute temperature), comprising:temperature characteristic compensating means for producing a control current of a value K2Ã—Tâˆ’(K1Ã—K2Ã—TÃ—Vcont/K3) according to the gain control current, the gain reference current and the bias current; and exponentially-changing current producing means, in which a first differential amplifier composed of a pair of transistors is arranged and bases of the transistors are connected to each other through a base resistor, for receiving the control current produced by the temperature characteristic compensating means at the base of one transistor of the pair of transistors of the first differential amplifier, for producing an exponentially-changing current corresponding to the control current and for controlling the variable gain cell according to the exponentially-changing current.