| 摘要 |
PURPOSE:To detect each burst signal through a smoothed capacitor, by using the detectors of double balanced connection in accordance with both NTSC and PAL systems. CONSTITUTION:The resonance frequency is set at 4.43MHz for a resonance circuit of L1 and C1 provided at the collector of the TRQ1 of a differential amplifier comprising the TRQ1-Q3. At the same time, the resonance frequency is set at 3.58MHz for a resonance circuit of L2 and C2. The detectors A and B of double balanced connection are connected to the collectors of the TRQ2 and Q3 via the emitter follower TRQ5 and Q7. The detectors A and B are connected together with balance by means of the constant current load of the common connection for the bases of the TRQ16 and Q27. The chrominance signals supplied from the terminals (c) and (d) are amplified with resonance to L1 and C1 or L2 and C2 and with the center frequency and turned into the output of detection after undergoing the peak detection through the detector A or B and then the smoothing through a capacitor C4. In such way, the burst signals of both the NTSC and PAL systems can be detected with just a capacitor. And an output of detection can be obtained at a terminal 4'. |
