Hello Emman,
Thanks for the reply. I've had a look at the video which was very interesting.
However, looking at the graphs and the equations I'm still not seeing where I'm violating any conditions.
With a Gain = 1, if -IN is set at 1.85V all the time and +IN swings from 0V to +2.88V then:
Vcm = 0.925V to 1.44V
Vdiff = -1.85V to 1.03V
With these values, none of the limits described in the equations are violated. I may be getting something wrong here!
One thing that's obvious is the non-inverting input voltage on A3 (difference amp in Figure 58 in the datasheet) is attemptedly being driven higher than +Vs. With a G=1, the input amplifiers are simply buffers so NODE 1 will go to 2.88V to which I'm trying to add a further 1.8V to equal 4.68V. Is this OK?
Thanks for your time.
Roger.