Hi,
I've found an issue whereby when a TLV70015DSE regulator is used to supply an op amp mid rail bias the reference 1.5V output is not stable and gradually rises to reach a voltage of approximately 2.18V.
On further investigation I found that op amps draw about 0.7uA but believe that the current is sourced from the op amp Vcc via the op amp long tail pair (Vcc= approx 3.0V) that seems to cause the regulator to voltage rise.
To try to prove this I replicated the op amp and replaced with a high value resistor of 2M2 to simulate a similar current. When this resistor was connected to the Vcc rail a similar effect with a rising voltage could be seen.
Note that the same 3.0V rail supplies the input of the TLV70015DSE regulator.
I found that the voltage could be made to return to the correct regulated voltage by connecting a 100k resistor from the 1.5V ref to ground. My thinking behind this was to provide a return current via ground to the regulator.
I would like some help to understand why this is happening as would assume that a regulator would be able to provide a solid voltage source o/p.
As far as I can see the regulator is connected as per recommended in the data sheet and with the recommended decoupling on I/P and O/P of 1uF ceramic capacitor. An outline schematic and circuit of the bal to unbal circuit are attached.
Thanks
Chris
