| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable gain differential amplifier circuit which can suppress variation in DC component included in the output voltage when the gain is varied. <P>SOLUTION: A variable gain differential amplifier circuit 12 comprises an amplification stage 12A and an adjustment stage 12B. The amplification stage 12A has differential circuits 13-15, and current sources 16a, 16b. Collectors of transistors Q3, Q6 in the differential circuits 14, 15 are connected with a power source line 20 via load resistors 18, 19, and collectors of transistors Q4, Q5 in the differential circuits 14, 15 are connected directly with the power source line 20. The adjustment stage 12B has differential circuits 21, 22, and current sources 23, 24. Collectors of transistors Q7, Q10 in the differential circuits 21, 22 are connected directly with the power source line 20, and collectors of transistors Q8, Q9 in the differential circuits 21, 22 are connected with the power source line 20 via the load resistors 18, 19. <P>COPYRIGHT: (C)2012,JPO&INPIT |
