| 摘要 |
1,196,323. Recording and playback; local circuits. AMPEX CORP. 16 May, 1967 [16 May, 1966], No. 16033/67. Heading G5R. [Also in Division H3] In a playback head and preamplifier arrangement having a magnetic playback head 10 connected to the input stage of a preamplifier 12, the frequency response of the connected playback head and preamplifier is substantially flat over a pass-band wide enough for video signals, the input stage has a lower impedance input than the impedance of the head's circuit and the preamplifier comprises a grounded emitter transistor input stage 13, a common base transistor intermediate stage 24 and a common collector transistor output stage 36 with negative feedback from the output stage to the base of transistor 13. The impedances of the input stage and head circuit are arranged such that a resonant peak of the head's circuit which occurs within the pass-band is swamped out. The input stage has a power gain which is sufficient to override noise contributed by following stages. The low input impedance of the amplifier is provided by a negative feedback path via capacitor 42 and resistor 41. The playback head may be used for reproducing signals from tape and is coupled to the input stage 13 by a rotary transformer 22. An emitter follower transistor 36 provides impedance matching of the output of the amplifier to a low impedance, coaxial cable 34. Reference has been directed by the Comptroller to Specifications 1,008,257 and 1,054,686. |
