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在电路设计中,经常遇到需将微弱的缓变信号放大的问题,而环境因素的影响及元器件的温漂会使被测信号难于辨认。例如,光电检测器件拾取微弱光信号时,就有环境光线及光电检测器件、前级放大器件温漂的影响。为此,有各种解决零漂的电路例如斩波、调制成交流放大及其他一些补偿的方法,但对于非电路环境干扰仍无作用。本文介绍一种在较短测量周期,工件物理参数测量时能采用的稳零放大电路。此电路利用测量的间隔稳零,结构简单,不仅能消除器件零漂,还能消除非电路部分的漂移,例如上述环境光线的影响。能在大于被测信号几倍的环境信号中(要求在检测间隔内环境情况不变)检出被测信号。电路如图1所示。 V_1为经过前置放大的输入信号(包括环境影响和漂移信号)。V_0为输出信号。在不测量的间隔时,V_0为高电平,则Y_4输出为低电平,Y_5输出为高电平。这样,T_1为通态(电阻约为几百欧),而T_2为断态(电阻为几十兆欧以上)。此时,若Y_1反相端有正信号输入(环境及漂移信号),Y_1即有一负信号输出,此信号经Y_2
In the circuit design, we often encounter the problem of amplifying the faint slowly changing signal, and the influence of environmental factors and the temperature drift of the components make the measured signal difficult to identify. For example, the photodetection device picks up weak light signals, there is ambient light and photodetection devices, preamplifier temperature drift effects. For this reason, there are various solutions to zero drift circuits such as chopping, modulation into AC amplification and some other compensation methods, but still have no effect on non-circuit environmental interference. This article describes a short measurement period, the workpiece physical parameters can be used to measure the zero-amplification circuit. The circuit uses zero measurement interval, the structure is simple, not only to eliminate the device zero drift, but also eliminate the non-circuit part of the drift, such as the impact of the ambient light. The signal can be detected in an environment signal that is several times larger than the signal under test (it is required that the environment conditions remain unchanged during the test interval). Circuit shown in Figure 1. V_1 is the preamplified input signal (including environmental effects and drift signal). V_0 is the output signal. In the measurement of the interval, V_0 is high, then Y_4 output is low, Y_5 output is high. Thus, T_1 is on-state (resistance is about a few hundred ohms), while T_2 is off (resistance is tens of megohms or more). At this point, if the Y_1 inverting terminal has a positive signal input (environment and drift signal), Y_1 has a negative signal output, the signal by Y_2