When the cathode/output voltage or current of TL43xx is being fed back to the reference/input pin in any form,
this device is operating in closed loop. The majority of applications involving TL43xx use it in this manner to
regulate a fixed voltage or current. The feedback enables this device to behave as an error amplifier, computing
a portion of the output voltage and adjusting it to maintain the desired regulation. This is done by relating the
output voltage back to the reference pin in a manner to make it equal to the internal reference voltage, which can
be accomplished via resistive or direct feedback.