A low noise voltage regulator circuit with fast stable output voltage is disclosed.
The low noise voltage regulator circuit contains a reference voltage generator,
for generating a reference voltage; a switching circuit, which is electrically
coupled to the output of reference voltage generator and has two states; and a
stabilizing circuit. When the switching circuit is at a first state, the reference
voltage is coupled to the stabilizing circuit without being filtered; when the
switching circuit is at a second state, the reference voltage is filtered by a
low pass filter before being coupled to the stabilizing circuit. A switching control
signal is used to switch the switching circuit between the two states. The filtered
reference voltage is used to generate a low noise regulated output voltage.