opamp design for integrator application

[dan11]

I need to design opamp for integrator application. Integrator feedback capacitor is a large off-chip 10 uF cap. Opamp slew rate (1st stage Itail/Cmiller) is very high. What are the design considerations for opamp output stage ? Do I need few mAmps in the output stage to drive this large integrator cap?

thank you !

 

[Dominik Przyborowski]

Use class AB push-pull output stage

 

[dan11]

Thanks Dominik. My question is what should be the calss A output stage current to drive the 10 uF feedback cap.

 

[FvM]

It solely depends on the integrator input current respectively input voltage and integration resistor. You should know it.

 

[dan11]

FvM, thanks but not sure I understand you.
Assuming integrator input and output voltage range 0-5 V , integrator input resistor is 1kOhm, integrator feedback capacitor 10 uF . What should be the integrator opamp calss A output stage current?

 

[Dominik Przyborowski]

It's a speed dependent. For example if you want to charge/discharge 10µF in full scale voltage 5V in 1ms time, You need 50mA of output current.

 

[FvM]

Assuming integrator input and output voltage range 0-5 V , integrator input resistor is 1kOhm

Just apply ohms law, 5V/1k = 5 mA