LM258: LM258

Hi Santosh,

santhosh ganta said:

The Below image representing type2 compensator non inverting type, while we are tuning Capacitor C1 some times LM258 IC showing improper behavior and functionality also not good.

So we need some suggestions about root cause and selection of feedback capacitor C1

It's impossible to give an answer with so little information, Santosh. Please specify "improper behaviour" and "functionality not good". What problems do you observe?

Please give way more details about your application. Do you have a complete schematic?

These threads may interest you:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/900929/tlv9004-tl9004-op-amp-output-voltage

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/905921/tlv9004-tlv9004-buffer-and-voletage-divider

Kai

Error amplifier 2 used as type 2 non inverting op-amp. Error amplifier 1 used just as voltage buffer.

The OP amp improper behavior means target signal IN2+ not able to tacking reference signal IN2-  when C7 is 1nf and C6 is  either 10nF or 1nF.

Functionality means virtual ground concept also not working when C7 is 1nf and C6 is  either 10nF or 1nF.

Hi Santosh,

C689 destabilizes your circuit and should be removed. See the links I gave you.

Kai

Hi Sir,

Thanks for reply.

I seen links which u have shared. Most of the ciruits are inverting with type2 compensator and capacitor also not mounted but they are used constant power supply for providing Vref(2.5V).

But in my case target voltage (50mV) is very less, so we need definitely voltage division section to reach target voltage. 

To provide constant precise voltage i mounted C689 near opamp IN2- pin. but sorry i didnt understand how it makes unstable please elaborate.

The links also so many circuits are there please separate which is suitable for this application.