I have a question about a op-amp circuit.
I saw a circuit where an op-amp is driving a transistor for a voltage regulator circuit.
There is 12-volts feeding both inputs but one input has a zener, the other has a resistor divider, etc...; both circuits are for maintaining a constant voltage.
The 12-volts also comes directly across through a resistor divider and in the middle is a capacitor with the other end connected to the output of the op-amp - which is also connected to the base of a transistor.
My questions are: what is the capacitor doing? If say the 12-volts goes through two equal resistors (for ease of explanation) and there is 6-volts DC on one side of the capacitor, what is this doing for the output of the op-amp?
Another words the the circuit would look like this:
op-amp output >>>>> capacitor >>>>> 6-volts (coming from resistor divider) >