circuit of improving linearity of photoelectric isolation device

Published:2011/6/8 7:09:00 Author:chopper | Keyword: linearity, photoelectric isolation device | From:SeekIC

We can improve the linearity of transmission of photoelectric couplers markedly by using inverse feedback.In the picture a,D1 is in the feedback path,the current through D1 will vary linearly with V1 strictly.The shortage of this circuit is that it don't consider the non-linear relation between current transmission of photoelectric couplers and operating current.Thus,careful selection is necessary as well as adjusting device.In the picture b,the circuit adds the second order feedback in order to improve the linearity.The gain frequency of the circuit is between 0~30KHZ,and the dynamic range is -8~+8V,nonlinear distortion(when it is ±8V)is less than 0.5%,weeping sound is less than 1mV,common mode voltage is more than 250V.



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