OPA455: Can i add output transistor to boost the output current ?

Hi,

theoretically, yes. But you would need to run a frequency respsonse simulation, a step response simulation and a phase stability analysis.

Keep in mind, though, that the output current of OPA455 is limited to +/-45mA. So, you would need transistors with high current gain to achieve a high output current. It may make sense to add a driver stage for the output transistor stage to not move the OPA455 outside of its SOA (safe operating area). This would be especially helpful when running the circuit with high supply voltages.

Kai

Hi PYTsai, 

PYTsai said:

Can OPA455 use below circuit to boost the output current and the target output is +/- 75V ? 

Could you provide us the driving application, current requirements and load type from the current booster circuit? As Kai pointed out, it should work, but OPA455 may not be able to swing up to ±75Vpk target, if this is the driving requirements. The designer is required to increase the supply rails to ±75Vdc for the OPA455 in the application. 

If you are able to provide us the design requirements, I can try to simulate the driving condition. 

If the ±75Vpk swing voltage are required, you may consider to use OPA462 with the similar topology, which it should give you the full output swing ranges up to ±75Vpk. And you would need to increase dual supply rails up to ±90Vdc in OPA462 as well (OPA462 is 180V part).

If you have additional questions, please let us know. 

Best,

Raymond

Hi Raymond,

Correct the requirement. out put +/-50Vpk is ok, output current Ipeak 400mA. Inormal 300mA . and output frequency is   45Hz ~ 90Hz

Does OPA455 look ok ?

Thanks! 

Hi PYTsai, 

PYTsai said:

Does OPA455 look ok ?

Here is the simulation, but you did not mention the circuit's application,  load type and other design requirements, where the op amp stability needs to be checked it out. 

There will be some crossover distortion, but it may be minimized. 

OPA455 100Vpp with BJT 03202023.TSC

If you have additional questions, please let us know. 

Best,

Raymond