OPamp configurations for high slew rate.

[Doug314]

I need an opamp configuration with the following specs. slew rate 14 v/us, Voltage range 18V, current output typically 1.5A or 5A peak. There are configurations one can use to achieve these results using multiple opamps, I assume. I need guidance on what type of configuration I would need to achieve these results.

 

[dougy83]

You can buy "power opamps" or "high-current opamps", e.g. https://www.analog.com/media/en/technical-documentation/data-sheets/lt1210.pdf (albeit peak current is only 2A). You can parallel the outputs for extra current capacity (and use current sharing resistors).

Alternately you can put a class B or AB output stage after a normal opamp.

 

[crutschow]

You cannot increase the intrinsic slew-rate of an op amp as given in their data sheet.
You have to buy one with sufficient slew-rate (probably at least 20 V/us if you need 14 V/us).

 

[dougy83]

You cannot increase the intrinsic slew-rate of an op amp as given in their data sheet.
You have to buy one with sufficient slew-rate (probably at least 20 V/us if you need 14 V/us).

You can add transistors at the output to increase the slew rate, and the GBW.

 

[crutschow]

You can add transistors at the output to increase the slew rate, and the GBW.

Only if you know how to compensate for the extra gain/bandwidth to keep the circuit stable.

 

[dougy83]

Only if you know how to compensate for the extra gain/bandwidth to keep the circuit stable.

It's not that hard. Here's an LM324, with the slew and GBW boosted:

 

[Doug314]

Thank you very much. I have learned a lot.

 

[schmitt trigger]

Dougy83;
Would you be so kind of posting the .asc file?

 

[atferrari]

Used to be not very expensive and easily available.

TL072, just 13 V/us

 

[unclejed613]

TL072, just 13 V/us

https://www.ti.com/lit/ds/symlink/tle2072.pdf
45V/us slew rate, 10Mhz GBW... pretty much a drop-in replacement for TL072.... just add output transistors for increased current... just make sure the miller capacitance of the transistors isn't too high and it should be plenty stable...

 

[dougy83]

Dougy83;
Would you be so kind of posting the .asc file?

Sure