I am wondering if possible to find an op-amp with high output current up to 600 mA. We have +/- 5 V available for biasing of the op-amp but the load requirement is 600 mA which I am not sure can be supported by op-amp or not. Any suggestion ?

 

Hi eng,
Does the OPA Circuit have to Source or Sink 600mA.?
E

 

A quick google search of power op amp finds this listing from TI.

https://www.ti.com/amplifier-circuit/op-amps/power/products.html

 

Hi engr
A basic OPA driving a power transistor [ with a low Vg ton] would provide a 600mA Source current.

E

 

Use push-pull output for higher current.

 

What is the Op-Amp's Output driving ?
.
.
.

 

How will a push-pull give a higher output current.

 

How will a push-pull give a higher output current.

By lowering the output impedance.

 

How will that lower the output impedance below that of a single ended current source when using a MOSFET with an Rds on, of 0.04 ohms?

 

How will that lower the output impedance below that of a single ended current source when using a MOSFET with an Rds on, of 0.04 ohms?

If the TS only requires a current source then your single MOSFET circuit will work.

 

your single MOSFET circuit will work.

....provided the required output voltage at the MOSFET source is less than the max output voltage of the opamp less Vgs.

 

I have asked the TS to confirm if he requires a Sink and/or Source current, let's hope he comes back with an answer.
Also, he has only +/-5V power available.
We need more details of the required output specification

E

 

There is nothing in post #1 to limit the output to sourcing only, so the circuit in #4 might not be adequate to the task.

A possible problem with the circuit in #5 is not impedance, but headroom. Most opamps cannot swing rail-to-rail, and a typical output headroom is +/-1.5 V. Add a small power transistor Vbe to that, and the circuit output range is only +/-2.9 V. The circuit in #4, aside from being unipolar, is even worse.

One way to do this is with the #5 circuit, but with common-emitter output transistors rather than emitter followers. Here is a concept schematic grab from later in the same article:



To the TS: What is the required peak or peak-to-peak output voltage range with respect to GND?

ak

 

How will a push-pull give a higher output current.

Because, generally speaking, that is what push-pull circuits do - ?

ak

 

How will that lower the output impedance below that of a single ended current source when using a MOSFET with an Rds on, of 0.04 ohms?

It won't necessarily reduce the output impedance, but it will certainly greatly lower the quiescent current.

 

I am wondering if possible to find an op-amp with high output current up to 600 mA. We have +/- 5 V available for biasing of the op-amp but the load requirement is 600 mA which I am not sure can be supported by op-amp or not. Any suggestion ?

Hi dear,
There are Opamps with high output carrent, but they usually are expensive.
For example LM759 (250mA) or PA51 (10A)...

 

op-amp with high output current up to 600 mA

All we have to work at the moment is the above, let's wait and see and see what is the required spec on compliance voltage etc is, then we can finalise a design.

 

Almost any audio power amp IC.

 

Thank you very much for your comments and all the replies. I am still working on getting more info on the requirement. I am sorry for not having enough information for now. But your comments and replies are valuable to me.

I also found this article describing how to buffer an op-amp output for higher current. I also have read the part -2 in which they introduce Darlington circuit to supply more current to the load.

https://www.allaboutcircuits.com/te...r-an-op-amp-output-for-higher-current-part-1/

 

I also have read the part -2 in which they introduce Darlington circuit to supply more current to the load.

Be aware that the Darlington arrangement drops the achievable output voltage by a further ~0.7V.