Frequency Compensation

[ambreesh]

Can someone tell me how we can insert a LHS zero in a system?

 

[amarnath]

Just add a miller cap as in a two stage opamp, this will introduce a zero since you now create another path for the signal to reach the output.Then try moving this zero to the right half if needed to improve your phase margin.

amarnath

 

[lijianheng]

Insert a resistor in series with the compensation capacitor.

 

[amarnath]

The resistor nullfies the zero if its sized such that it cancels out the zero created by the miller cap. The resistor can also be sized to move the zero to the right half plane to increase the phase margin.


amarnath

 

[ambreesh]

Yes, method of nulling resistor along with the cap in series is know well.
But do we have any alternate method of adding LHZ.

I think it was a typing mistake , we would not like the zero to be RHS as it is going to deteroriate te phase margin.