I am using a number of single-supply op-amps (OPA4344) in a circuit, and am using one of them to supply a VCC/2 value for a virtual ground to the + side of several other op-amps.
VCC is +5 volts. When I first power up the board, I get 2.5v from the output, but after awhile the output jumps to around 4.5 volts and stays there until I power off and back on again.
I read here that:
Due to the strong (i.e., unity gain) feedback and certain non-ideal characteristics of real operational amplifiers, this feedback system is prone to have poor stability margins. Consequently, the system may be unstable when connected to sufficiently capacitive loads. In these cases, a lag compensation network (e.g., connecting the load to the voltage follower through a resistor) can be used to restore stability.
As you can see, I am already using a resistor on the output. The datasheet for the 4344 (referenced earlier) claims the op-amp is "unit gain stable."
Is there something else that can be causing the instability? Do I need a separate resistor for each output (currently I the + inputs of three op-amps tied to VOUT).