On Mon, 14 Jan 2008 10:28:03 -0500 Spehro Pefhany wrote: > I think that would be "all", not *some*. unless the op-amp somehow > generates a negative voltage internally. Even if the CM range includes > ground (or a few > hundred mV below ground) the Vos could be negative by a few microvolts, > and the *output* cannot go below ground without a negative supply > *somewhere*, so the op-amp cannot balance. There are quite a few opamps that have pnp transistors on the inputs and allow (slight) negative excursions (LM324 comes to mind). Others have JFET or MOSFET at the inputs and also work around 0V. Also balancing is not the point - the OP wanted to know how to tie off an unused amp. John -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist