| 摘要 |
1,272,962. Automatic gain control. RCA CORPORATION. 17 July, 1969 [22 July, 1968], No. 36132/69. Heading H4R. [Also in Divisions G4-G6] Each amplifier connected to a photo-cell reading a respective track on an optical record (see Division G5) includes an a.g.c. circuit 47 to standardize the amplifier outputs when the photo-cells scan reference zones in each track. The photo-cell signal at 51 is amplified in operational amplifier 52 whose output 53 is connected to another operational amplifier 55 arranged to conduct when the output 53 is more negative than a -3v reference voltage 66. This charges capacitor 57 to cause MOS transistor 59 to conduct and control the negative feedback of amplifier 52 via resistor 60. The a.g.c. may be switched by gate 50 to operate only when the reference zone is scanned. The output from power amplifier 48 is sampled in gate 49 so that the several outputs may be combined e.g. to synthesize speech. |
