. RF summing and auto gain control circuit in digital versatile disc player system

摘要

PURPOSE: An RF signal summing and automatic gain control circuit of a digital versatile disk player system is provided to automatically control amplification gain even if the magnitude of an input signal varies and to enable accurate reproduction of data in a DVD player. CONSTITUTION: An RF summing and automatic gain control circuit includes the first amplifier(40), at least one variable resistor(RV42,RV43), an interface circuit(47), and the second amplifier(42). The first amplifier sums up RF signals applied through at least one input ports, and amplifies the summed signal by a predetermined amplification gain. The variable resistor varies the resistance value in response to a predetermined resistance control signal to adjust a resistance component between the input port and an output port. The interface circuit decodes a predetermined n-bit signal applied from the outside to generate a resistance control signal. The second amplifier amplifies the output signal of the first amplifier and outputs the amplified result.