What is stability or Right-Half-Plane

[richardyue]

Who can tell me what is stability? I often see the right-half-plane used to determine whether a circuit is stable. Who can tell me how to use this technology and what it is?

 

[kender]

Look up "root-locus".

 

[safwatonline]

try to think of exp(at) where is a constant
now if u r in the RHP then a is positive which means that the signal increase with time which means no stability
on the other hand if u r in LHP then a is -ve which means that the signal decrease with time "stable"

while when u r on the sigma=0 then a=0 which means that the signal is neither decreasing or increasing

note , i mean inc. and dec. in transient

 

[hubert008]

I think you should read some books, there are many books which talk about it.

 

[safwatonline]

Hi,
i saw this and thought it migh help to explain what i meant in my previous post

 

[260278]

?

 

[lavitaebelle]

Any signal, in the time domain, will have a steady state response and a transient response. The transient response decides whether the signal is stable, unstable-fast settling, ringing,etc. The frequency domain transfer function is nothing but the same time domain signal transformed into the frequency domain.
Now looking at the poles gives an idea of the transient response of the signal. Left half plane pole translates to a decaying exponential signal and Right half plane pole translates to a growing exponential signal and hence unstable. (because theoretically at t=infinity, the signal amplitude is infinity).

 

[ithink]

stability is very important to close loop system,such as op amp,pll. there are a lot of methods to solove, such as root locus,bode plot. but they are different, u have to select one that you like. if you don't know what i said, please refer to book <<signal and system>> and read s domain introduction. i hope u can look for the answer about zero and pole in this book.

 

[shaikhsarfraz]

Stability is an important criteria for analog circuits.
If the system is not stable, then there are chances that sustained oscillations will produce in the output for a feedback system.

This can be explained simply as follows

if we have right half poles it will be like

s+jω

The time domain response for such poles is like

exp(st) [cos(ωt) + j sin(ωt)]


For left hand plane pole

(-s+jω)

The time domain response for such poles is like

exp(-st) [cos(ωt) + j sin(ωt)]

From these to time domain responses you can see that the oscillations in the case of Left hand plane poles will die off with time and we will get stable output

Regards
Shaikh Sarfraz

 

[huojinsi]

shaikhsarfraz's explanation is very perfect!

 

[doremon]

For Oamp, amp...Stability is important, If the circuit is not stable the output for feedback system will has oscillations so stability is very important to close loop system, We need take case Zero point and pole poit and response about frequency for this pole point and zero point. If In region Laplats, RHP is like (S+ jw) then LRP is like (-S+jw) so we only caculate for RHP we can to find out for LHP.

 

[aborigini]

You can try to read some ic desing textbook. Can try razavi book on stability.

Stability is very important in close-loop system as in op-amp application. I think just do some reading first.

 

[shake2004]

you should read such books as "modern control" first.

 

[beckchm]

just use inverse-laplase transformation