500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}" onclick="if(!this.resized) {return true;} else {window.open('http://u.dianyuan.com/bbs/u/40/1144031988.gif');}" onmousewheel="return imgzoom(this);">
图中R2是干什么用的?另外还想问VD3和VD4是阻尼二极管吗?
