Hello,
I am using two separate power supplies to provide ±15VDC to the op-amp. Being unable to start them simultaneously, there is a delay of roughly 100ms between the start of the first supply (+15) to the start of the second supply (-15). Could this delay possibly damage the op-amp, or are they designed to handle this scenario?
Thanks,
HSG
Hi,
as long as the absolute maximum ratings of TLE2144 aren't violated, there will not be any problem.
But take care that the supply voltage regulators have latch-up protection diodes at their outputs as shown in this schematic:
Why this?
Every OPAmp consumes supply current from the positive and the negative supply voltages at the same time. So, if the +15V supply voltage comes first, the OPAmp would try to push its supply current into the output of negative voltage regulator, forcing a positive potential at the output pin of negative voltage regulator. This can block the negative voltage regulator and can make it trap into latch-up. The (lower) latch-up protection diode limits this positive voltage, shunts the associated current arround the output of negative voltage regulator to GND and prevents latch-up. The same story is true, if the -15V supply voltage comes first. Then, the upper protection diode prevents the positive voltage regulator from trapping into latch-up.
Kai
Hello High-Speed Guy,
Many Op amps are reasonably immune to power supply start-up timing differences, but some are not. Its not the kind of thing that is usually discussed in the datasheet because the assumption is the supplies will come up to level at about the same time. One hundred milliseconds doesn't seem long us, but to a dual supply Op amp odd things might occur during that time so it is best to try and minimize the issue.
One remedy that we recommend and helps avoid the possibility of odd thing happening with supply start-up delays is to add transient voltage suppressor (TVS) diodes to each of the supply pins as shown below. The unidirectional TVS diode operates in a similar fashion to a Zener diode. The TVS diode on the power supply line that comes up later will be momentarily forward biased and provides a current path to ground. Once that supply comes up to voltage the TVS will be reverse biased and all should be good with its supplies as far as the Op amp is concerned.
Regards, Thomas
Precision Amplifiers Applications Engineering
