Videoverstärker

摘要

1,038,634. Transistor amplifying circuits. SPERRY RAND CORPORATION. Sept. 3, 1963 [Sept. 7, 1962], No. 34736/63. Heading H3T. [Also in Division G4] In a character reader an amplifier for the video output of the scanner consisting of character data signals and blanking signals comprises a number of transistor stages the last of which is connected to a shunt gate adapted to remove the blanking signals. The characters are sensed by a camera tube scanner making a number of parallel scans through the character. The flyback is blanked so that the photo-cell output contains blanking signals 82, Fig. 3 (not shown), at each end of a scan and data signals 84 between. When a group of five characters are scanned, there being about ten scans as illustrated in Fig. 3 (not shown), for each character, the composite video signal is as illustrated in Fig. 4 (not shown), the scan groups being at 841 and the blanking signal envelope as shown at 82. The video signal is applied through potentiometer 22, Fig. 1 (not shown), and capacitor 24 to amplifier transistor T1. The output is passed to the base of second stage amplifier transistor T5 through capacitor 36. The output of T5 is applied through capacitor 42 to the bases of T3 and T4 to obtain the signal of Fig. 5 (not shown), the base line 49 being substantially unchanged but the other signals being much amplified. Transistor T3 serves to charge the capacitor 48 to the most negative input signals, i.e. base line 49, and this is applied through transistor T2 and resistor 54 to the base of transistor T4 so as to be subtracted from the amplified video signal. The output of T4, Fig. 7 (not shown), is applied through capacitor 58 to transistor T6 connected as an emitterfollower. The output is modified by shunt gate T7 which is operated at blanking times to short out the blanking signals 82, leaving the character signals only as in Fig. 8 (not shown).