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本文介绍用于脉码调制(PCM)系统的厚膜RC有源滤波器。 PCM电话传输系统用的滤波器要求体积小和生产成本低,并具有良好的性能。 介绍的滤波器是十二引出线单列组件。尺寸是厚5毫米,高10毫米及宽30毫米。它们满足D3—信道处理单元的各项需要。 发讯滤波器是七阶带通滤波器(BPF)。收讯滤波器是五阶低通滤波器(LPF),且附有—RC输入级作为有损耗的取样和保持电路。 为完成微型化,厚膜电阻印制在氧化铝基片的一边。在另一边,装有四端运算放大器和单陶瓷片电容器的一块集成块。 考虑到经济的生产,滤波器设计具有下列特点: 1)只用了数值相同的一种电容器; 2)为了得到优质产品,采用了对电路元件敏感度低的多种回授线路; 3)采用由电子计算机控制的激光微调装置进行快速确定的调整方法。
This article describes a thick film RC active filter for pulse code modulation (PCM) systems. Filters for PCM telephone transmission systems require small size and low production costs with good performance. The filter introduced is a twelve-lead single-column assembly. The dimensions are 5 mm thick, 10 mm high and 30 mm wide. They meet the needs of the D3-channel processing unit. The transmit filter is a seven-band band-pass filter (BPF). The receive filter is a fifth-order low-pass filter (LPF) with a -RC input stage as a lossy sample and hold circuit. To achieve miniaturization, a thick film resistor is printed on one side of the alumina substrate. On the other side, a manifold with a quad terminal op amp and a monolithic ceramic capacitor. Considering the economic production, the filter design has the following characteristics: 1) Only one kind of capacitor with the same value is used; 2) Many kinds of feedback circuits with low sensitivity to circuit components are used in order to obtain high quality products; 3) Electronic computer-controlled laser trimming device to quickly determine the adjustment method.