PROTEUS中有对数运算放大器模型吗？
请大侠明示，谢谢 y 请问millwood0 能告知我哪个模型好吗？？我急着用，谢了 proteus中无对数放大器模型,其它软件如Pspice,multisim等都没有.saber中有无就不知道了.下面列了AD公司的对数放大器型号.你如有其它知道的型号,我可帮你广泛查一查.AD606，AD640，AD641，AD8302，AD8306，AD8307，AD8309，AD8310，AD8315，AD8311，AD8312，AD8313，AD8314，AD8317，AD8318，AD8319，ADL5513，ADL5519 "请问millwood0 能告知我哪个模型好吗？"
any opamp + any diode. a p-n junction's forward voltage drop and its current flow follow a log relationship:
Vf=log(Ifwd).
the relation is more accurate at small current levels.
so you can easily construct a log amp using a diode (or a transistor configured as an amplifieddiode).
http://cache.amobbs.com/bbs_upload782111/files_16/ourdev_452291.PNG
(原文件名:log amp.PNG) millwood0 是个热心肠的好人，在下非常佩服！！！ 我的直流扫描怎麽是一条直线？？？http://cache.amobbs.com/bbs_upload782111/files_16/ourdev_452371.GIF
(原文件名:未命名1.GIF) 是不是我还有地方没设好？？不解啊，还是麻烦millwood0 帮助一下啊！！ here is the sim file.
点击此处下载 ourdev_452443.rar(文件大小:17K) (原文件名:Log amp.rar) 楼主用原理电路学习仿真一下还可以.如实际应用要考虑漂移等因素.因此电路就不会那么简单.如工程应用建议还是采用专用对数放大器.下面是早年在失真度测量仪电路中用运放和分立元件构成对数放大器的一个例子.http://cache.amobbs.com/bbs_upload782111/files_16/ourdev_452493.jpg
(原文件名:log amp.jpg) eezm's circuit is essentially two simple log amps combined together to cancel their tempco. A8 is the one generating the output. A9 and the right half of ua726 forms the 2nd log amp: its output depends will go up and down with temperature. However, that signal is applied to the left half ua726's emitter, making it out ofphase with A8's output, thus canceling out the tempco impact.
another approach is to build two identical log opamp (using a lm394 + a dual opamp), and use a differential amp to subtract the temp - caused thermal drift.
if you don't want to use matched pairs, you can replace the 1k resistor with a thermister with positive tempco (at +0.2mv/c) to offset the negative tempco from the diode / transistor. 首先谢谢millwood0 ；eezm 两位前辈
现在找到了一种可用的对数运放 LOG112/LOG2112，供货商提供了原理图文件及模型文件，听说是用PSPICE软件打开的，但原理图总是打不开，现在上传其原理图文件及模型文件，看看能否转为PROTUES模型？？点击此处下载 ourdev_452512.rar(文件大小:6K) (原文件名:log112.rar) spice 模型可很容易导入到ORCAD的PSPICE中使用,如何导入到PROTEUS还不清楚.
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