A fast reference circuit having active feedback includes a bias supply
circuit and a variable divider circuit connected by an active feedback
path to the bias supply circuit, and a comparator circuit connected to
the variable divider circuit, the bias supply circuit, and a reference
node of the variable divider circuit. In one embodiment, a start-up
circuit initially discharges a potential at the bias supply and
comparator circuits, then initializes a reference voltage at the
reference node at about zero volts to improve repeatability. In one
embodiment, the variable voltage divider comprises an impendence that is
trimmed based on a sheet resistance of a process used to fabricate the
fast reference circuit, and further comprises a variable reference
current circuit coupled to the impedance and configured to generate a
current having a value based on a desired reference voltage and to
conduct the current through the impedance, thereby generating the
reference voltage associated therewith. The comparator circuit is
configured to compare the bias supply voltage to the reference voltage,
and drive the bias supply and the variable divider circuit in response to
the comparison, thereby quickly stabilizing the reference voltage.