论文部分内容阅读
随着电视机生产量的不断扩大,用于自动增益控制电路(AGC电路)中具有AGC特性的高频晶体管(AGC管)参数的判别与检测显得愈来愈重要.我们知道,天线输入的高频电视信号在电视机的高放级得到放大,经混频后变成中频信号并经中频放大后再送到视频检波得到视频信号.然而,由于电视机的输入信号电平往往是不稳定的,所以必须用AGC电路来克服这种不稳定,从而保证电视机的正常工作.图1为AGC电路方框图.由图可见,由预视放管取出的图象信号电压,首先通过取样检波电路变成直流电压,并经AGC电压放大后去控制第一、二中放管及高放管的增
With the increasing production of TV sets, it is more and more important to judge and test the parameters of the high-frequency transistor (AGC) with AGC in the AGC circuit. We know that the antenna input is high The frequency television signal is amplified in the high-level television set, and after mixing it becomes the intermediate frequency signal which is amplified by the intermediate frequency and sent to the video detector to obtain the video signal.However, since the input signal level of the television set is often unstable, Therefore, AGC circuit must be used to overcome this instability, so as to ensure the normal operation of the TV. Figure 1 shows the block diagram of the AGC circuit. As can be seen from the figure, the image signal voltage taken out by the pre-amplifier is first changed to DC voltage, and after the AGC voltage amplification to control the first and second in the tube and high tube increase