OTA driving stage for driving high capacitive load with reasonable Slew rate

[Junus2012]

Hello

if we have a large capacitor load in term of some PF, then we need to use output stage for the basic OTA to be able to drive it with enough current for the slew rate without disturbing the biasing current of the core amplifier.

Perhaps you read the above sentences in different literature, but whenever I use the driving or the output stage I need to use a compensation capacitor C.C then again the slew rate is limited by the C.C and again we need to supply it with enough current especially if the CL is large then C.C will be also large, my question is '' what the driving circuit did for us in case of driving large CL with high S.R "

Thank you all

 

[erikl]

It is possible to construct an OTA so that the compensation is achieved by the load capacitor, so no Miller compensation is necessary. See the appended tutorial, pp. 10 ff.

 

[Junus2012]

first Thank you for your reply

Yes I am doing this in my project, I designed folded OTA and balanced (symmetrical OTA) with self compensating, but if would add class AB stage to the output then I must add the compensation capacitor also and this will be problem if the load is C is very high .

It is possible to construct an OTA so that the compensation is achieved by the load capacitor, so no Miller compensation is necessary. See the appended tutorial, pp. 10 ff.

 

[erikl]

... if would add class AB stage to the output then I must add the compensation capacitor also and this will be problem if the load is C is very high .

In this case, this paper might be helpful: