A differential circuit system is provided. The differential circuit system includes: a different circuit set including a plurality of differential circuits, a voltage regulator, and a current drainage circuit set. The differential circuits are electrically connected between a first node and a second node, and each differential circuit generates a current flowing from the first node to the second node. A high voltage is provided to the first node and a low voltage is provided to the second node. The first node receives an external voltage. According to the first voltage, the voltage regulator generates the low voltage. The low voltage is provided to the second node. The current drainage circuit set generates a drainage current in between the second node and a ground voltage. A superposed current flowing to the voltage regulator is difference of the summation of currents minus the conducting current.