OPA170 / rush current at the time of switching on of power supply

Kato-san,

It is common for op amps to exhibit a surge current behavior during power up. The surge current is usually a function of how quickly the supply voltage moves from 0 V to the final value. 

We have not characterized the transient turn-on current of the OPA170, but I did speak with some of our design team members about your question. I was told that based on the normal operating current and its slew rate they estimated the current could be as high as 5x. For a typical operating current of 110 uA, for a 1 ms, the surge should be under 600 uA. However, do note that if you use the recommended 100 nF power supply capacitor from V+ to ground, the current it alone  requires during the 1 ms power can be a significant factor. From:

i = C dV/ dt 

i = (100 nF) [(36) V / 1 ms] = 3.6 mA

That is certainly higher than the OPA170 would draw during the 1 ms turn-on event. 

Regards, Thomas

PA - Linear Applications Engineering

Hi Thomas - san,

Thank you for the reply. I understand the surge should be under 600uA for a 1ms slew rate. In this case, what is the peak of output voltage overshoot?

Best Regards,

Kato

Kato-san,

Unfortunately, we do not have that information.

Regards, Thomas

PA - Linear Applications Engineering