Class AB 经典架构的问题

xiaoxianzai

1  这篇经典论文中讲到 ：同相I1和I2输入，为什么M20电流会增加呢？M19电流会减小呢？IB7和IB6是恒定的，那么流进来的电流I1和I2跑哪里去啦？
高手帮小弟解释下这个电路的工作原理  谢谢啦

bsaqycx

I1 and I2 are not the same phase I think. The detail discuss is already there:  
http://bbs.eetop.cn/viewthread.p ... ;extra=&page=1.
Hope it helped

longqingshan

i1 and i2 肯定为相反的电流。假设a端流入正向电流，则a端电压升高，b端也由于注入更多的电流电压升高。直至电流全部从M20流过而M19关断，此时b端电压甚至可升高至与a端电压相仿；反之亦然；故输出级可产生很大的slow rate；这是一个过程分析；
小信号分析时，可认为A端B端之间具有很小的电阻而可视之为短接（这个你可以单独拿出M19 M20，用小信号模型分析一下）。
从a或b端看上去的电阻很大，故只要只要很小的电流差值（i1-i2），便可使A端或B端产生很大的电压摆动。

longqingshan

I1and I2 肯定为变化趋势相反的电流，亦即大信号上叠加的小信号电流方向相反。

sdmout

Iin1 and Iin2 are inphase, but only voltage shifted to avoid cross distortion. Actually the class AB coupling is very strong in this design, and can be driven by only one input (i.e. either Iin1 or Iin2). The cool thing is that there is a minimum current control, so that no output transistors are completely turned off.

This circuit also works for bipolar design.

For details, search "translinear circuit" developped by Gilbert.

司徒温孤

学习了啊！！

sdmout

Actually many class AB output stage design utilises a minimum current selector in both bipolar and MOS processes. This head-to-tail coupling design is the most elegent one.
The important feature is that no output transistors (M25, M26) are completely turned-off, improving the speed and stability.
Also the class AB coupling is very strong, (i.e. no current leakage between M19, and M20), so that it can be driven by a single input. This enables fully-differential opamp designs.

yueqianglxiaxia

yun zi ji duo kan kan jiu zhi dao le

gaojun927

study

lsts1211

study