At 11:27 PM 10/18/99 -0400, Sean wrote:
>How can a non-inverting follower work without at least a negative supply? I
>interpreted "negative reference" to mean "negative supply" in this case.
>
>If we could use an inverting buffer, THEN it wouldn't need a negative
>supply. However, good luck finding a high enough Rin,

As far as I know, you never need to have bipolar supplies. You just need a
Vss and a Vdd and a common point in between, typically at the midpoint.

The common voltage becomes the signal ground. The full Vcc becomes the
'plus' voltage. The power supply ground becomes the 'minus' voltage.

This works for all op-amps, although rail-rail types are best suited to low
voltage supplies, such as the 5 V needed in the example.

To connect the pH electrode to a non-inverting voltage follower with a
LMC660, connect one side to the non-inverting input and the other side to
the common point (@ 1/2 VCC). Feedback the output to the non-inverting
input. Voila!

What's the problem?

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