2018-10-08

2018-10-08

作者: carpediemmlf | 来源:发表于2018-10-09 23:32 被阅读0次

Modelling non-ideal operational amplifier

gain
$Z_{in}$
$Z_{out}$

Non-idealness

A is not $\infty$ but $10^4 \sim10^6$
$Z_{in}$ is not $\infty$ , $Z_{out}$ is not $0$
complex $A(\omega)$

Non-ideal non-inverting case

Added $r_{in}$ and $R_{out}$
Conserve current and use Ohm's law
$V_{out} =V_{in}\cdot {(open\ loop\ gain)} - i_{out}\cdot {(output\ impedance)}$

For large A, high $r_{in}$ and low $R_{out}$

$gain = 1+\frac{R_2}{R_1}$
$Z_{out} \rightarrow \frac{R_{out}}{A}(1+\frac{R_2}{R_1})$
$Z_{in} \rightarrow \frac{r_{in}A}{1+\frac{R_2}{R_1}}$ , which reaches $10^{12} \Omega$

$gain = 1$ when $R_2 = 0$ , this is a "buffer" to send signal from system into another device without affecting the system
Inverting case

$gain = -\frac{R_2}{R_1}$
$Z_{out} \rightarrow \frac{R_{out}}{A}f(\frac{R_2}{R_1})$
$Z_{in} \rightarrow R_1 + low\ valued\ f(\frac{R_1, R_2, V_{in}}{A})$
use a non-inverting one to achieve high input impedance

Over a large frequency range, the phase shift of the feedback could become $\pi$ s.t. negative feedback becomes positive feeback and leads to saturation/oscillation. This is countered by built in reduction of A.
Interlude on feedback
$Output = A(input + \beta input)$

相关文章

网友评论

本文标题：2018-10-08

本文链接：https://www.haomeiwen.com/subject/nuoyaftx.html

延伸阅读

深度阅读

您也可以注册成为美文阅读网的作者，发表您的原创作品、分享您的心情！

栏目导航

热点阅读

关于我们|服务条款|联系我们|2018-10-08|投稿指南|网站地图|RSS订阅|排版工具|手机版

提供经典美文摘抄,优美散文欣赏,现代诗歌精选,短篇小说,心情随笔,表白情书范文,故事会在线阅读欣赏

Copyright © 2014-2023 Haomeiwen.com All Rights Reserved. 好美文阅读网版权所有

备案信息：桂公网安备 45052102000051号 · 桂ICP备13007215号-3

本站所收录作品、热点评论等信息部分来源互联网，目的只是为了系统归纳学习和传递资讯

所有作品版权归原创作者所有，与本站立场无关，如不慎侵犯了你的权益，请联系我们告知，我们将做删除处理！