Hi ,
I have used 2 OPA827 to build a 2.5mA current source in my design.
a coto relay is inserted inbetween to cut out the current source when it is not used. my problem is that one of OPA827 is from time to time got destroyed.
any idea when this damage comes from? Relay switching?
Hi Robin,
The damage is very likely caused by the relay switching with insufficient protection around the op-amps. I would recommend adding 1kOhm resistors at the inputs of your second OPA827 as shown below to limit the current into the internal ESD diodes during a transient. I would also recommend adding TVS diodes across your power supplies to prevent a large surge from latching the internal op-amp absorption devices. If you do not have local bypass capacitors on your op-amp power rails it would be good to add these as well. 0.1uF is generally sufficient.
Additionally, depending on the range of your loads, particularly for the inductive loads, you may have stability issues. If you can bound your loads I can look into whether this is the case
