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4.信号源与其输出控制部分 (1)音频信号发生器信号发生器的框图和线路图如图8和图9所示。信号发生器是采用两级分差电路与RC桥臂组成的文氏电桥振荡器。首级分差采用高耐压配对场效应管,具有低噪声、高输入阻抗、振荡稳等特点,桥臂的元件都经过严格挑选,上下臂配对,以增加振荡稳定度,减小非线性失真。前置单端推挽输出通过一高灵敏的热敏电阻负反馈到首级,起自动稳幅作用,末级功放采用两块TDA型集成电路,具有高增益、失真小的功能。由于振荡器采用较先进的电路,电路简单且挑选了精良的元器件,使它工作十分稳定,具有长期连续工作能力,经两年使用,性能可靠。共主要技术指标如下:
4. Signal Source and Output Control Section (1) Audio Signal Generator The block diagram and the wiring diagram of the signal generator are shown in Figure 8 and Figure 9. The signal generator is a Wien-bridge oscillator composed of two stages of difference circuits and RC bridge arm. The first level difference using high voltage matching FET, with low noise, high input impedance, oscillation stability and other characteristics of the bridge arm components have been selected, the upper and lower arm pairing to increase the stability of the oscillation and reduce the nonlinear distortion . The front-end single-ended push-pull output is negatively fed back to the first stage through a highly sensitive thermistor, which automatically stabilizes the amplitude. The final stage uses two TDA integrated circuits with high gain and distortion. As the oscillator uses more advanced circuits, the circuit is simple and select the excellent components, make it work very stable, with long-term continuous working capacity, after two years of use, reliable performance. The main technical indicators are as follows: