Other Parts Discussed in Thread: OPA627
TL072C input voltage VDD15V VSS-15V
Temperature is ok
After sometimes , I found IC broken , VDD and VSS is short circuit. I want to know why the phenomenon occurs 3 times .
schematic:
TL072 make a buffer .
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May I assume that this happened on three different boards that were in use for a long time by the final customer? Please attach the schematic again as it did not work correctly. I suspect over stress from power supply or Electrical Static Discharge any board connectors that connect to the op amp. Is this true?
There are two ways (green squares) to insert a file or picture, I prefer the one of the left. Please attach the schematic again.
Thanks . The phenomenon on the same board three times .The reason always is short circuit by VDD and VSS pins .diffamp.pdfdiffamp.pdf
Nobody can touch this IC because it have a box . I check the resistance for 3 broken IC. The value is 158Ω ,68Ω,20KΩ.The new IC is 400kΩ. between VDD and VSS. I want to know the correct value between VDD and VSS.
Hi,
I would add a protection circuit (diode clamps to the supply rails) to the output of TL072, similar to the input protection of OPA627.
Kai
Thank you . In my view . Maybe TLO72 is in order to protect OP627.
I appreciate your view .Look forward your schematic.
The TL072 are driving the cable shield and the cable can be touched. I like Kai's idea of the series resistor and diode to supply pins. If this happen three times on same board and other different boards work normally, then there must be something different about this one board. One possibility is that the op amp is being installed backwards (clocked 180 degrees).
For a device check, use the diode feature of the DMM. Check VDD and VSS pins in both polarities and compare suspect device with a new device.
I really appreciate your help. By the way ,I want to know the function about TL072,I think maybe it is protect OPA627,Because OPA627 is expensive.
I appreciate your help.I suspect the data is TL072 can acceptable voltage is 16.8 to 19.1 not Steady-pressure value of the Zener diode .So you suspect the input voltage maybe too high can damage the TL072.
Hi,
the purpose of TL072 is not to protect the OPA627, but to bring a buffered copy of the input signal onto the cable shield. By this the input signal sees a much smaller effective cable capacitance.
Kai
Thanks.
The TL072C input voltage 15V and -15V from iner Power board. Your view is Power board supplying VDD and VSS too high , So the TL072 is broken .
If the TL072 keeps breaking, then I suggest to remove the op amp and run the system without the op amp then measure the voltage on all 8 pin pads and see if anything is odd.