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本电路用光电耦合器在金星C37-401彩电上安装视频、音频输入接口。整个装置由于不用隔离变压器,所以使用方便,而且电路简单,传输的彩色图像清楚,伴音宏亮,信号质量高于射频传输方式。电路原理图如图1所示。 (一)工作原理从录像机输出的视频信号,通过75Ω同轴电缆送到输入端Q_1,由BG_1放大后经光耦合器耦合到BG_2上。这里采用二极管-二极管型光电耦合器,主要是为了提高工作频率。调整R_2可使光耦合器得到合适的工作状态,防止图像信号失真。C_2是频率补偿电容,客量在2200～5100pF之间选用。BG_2、BG_3是直接耦合放大器,经电阻R_6、R_8加上反馈,R_7的大小决定
The circuit with a photocoupler in Venus C37-401 TV to install video and audio input interface. Because the whole device does not need to isolate the transformer, it is easy to use and the circuit is simple. The transmitted color image is clear, the sound is loud and the signal quality is higher than the RF transmission mode. Circuit diagram shown in Figure 1. (A) Working Principle The video signal output from the video recorder is sent to the input terminal Q_1 through a 75Ω coaxial cable, which is amplified by BG_1 and then coupled to BG_2 via an optical coupler. Diode - diode type optocoupler here, mainly to improve the operating frequency. Adjust R_2 optocoupler can get the appropriate working condition, to prevent distortion of the image signal. C_2 is the frequency compensation capacitor, the customer’s choice between 2200 ~ 5100pF. BG_2, BG_3 is a direct coupling amplifier, the resistance R_6, R_8 plus feedback, R_7 the size of the decision