Note: For proper action, the input
of the non-inverting opamp should
be referenced to ground if using a
bipolar supply. If V- is ground, then
the input resistor must be referenced
to 1/2 V+.

To convert to db,
db = (Vg)log X 20

also

db = 20 log Eout/Ein
or
(Eout/Ein)log X 20