application of unstable amplifer

[Jenifer_gao]

Hi All:

I may ask a stupid quesion, but it bothered me for long time. Now I have a system with phase shift of 185°, as a result this system will becomes unstable. I could do some compensation for this system, but it will increase the power. Because power in my design is very strict. I used this system to do a step response simulation with a unity gain feedback configuration. I find it will give me more ringings than that of small phase shift. So I think this big phase shift only affects the settling time. If my system has a relaxed requirement for the settling time, and it is only applied in the large signal step response, this system may still be feasible.
So far I only see the drawback of settling time. If anyone can point out what else harmness of this unstable system in a large signal applicaion. Thanks.

J

 

[Btrend]

if noise is white, then it will "inspire" ur system to "oscillate" at the PM=0, (positive feedback configuration).

 

[eng_Semi]

if noise is white, then it will "inspire" ur system to "oscillate" at the PM=0, (positive feedback configuration).

I agree with these words, also u will have an output which don't relate to the input, not some ringings as u imagine, it will be a completely oscillating output

 

[Jenifer_gao]

Thanks for all replies. You are absolutely right. I have to include the compensation.