| 摘要 |
PROBLEM TO BE SOLVED: To provide a demodulation circuit, capable of demodulating the received signal of digital satellite broadcasting as is by providing the active inductance circuit having characteristics similar to there of a coil and a filter circuit using the active inductance circuit. SOLUTION: An active inductance element is constituted by serially connecting transistors Q1 and Q2 and transistors Q3 and Q4, which compose differential pairs, providing a capacitive impedance element ZC between the emitters of the transistors Q1 and Q2, providing a resistor R3 between the emitters of the transistors Q3 and Q4, connecting the base of the transistor Q3 to the collector of the transistor Q4, connecting the vase of the transistor Q4 to the collector of the transistor Q3, connecting the base of the transistor Q1 to the collector of the transistor Q2 and connecting the base of the transistor Q2 to the collector of the transistor Q1. By the use of this active inductance, a filter having sharp characteristics can be provided. |
