Abstract: An LED driver according to the present invention feeds an electric power to an LED circuit, which is either of a single LED or a plurality of LEDs serially connected together. The LED driver includes: a constant current circuit part serially connected to the LED circuit and adjusting a current flowing from an upstream to a downstream side thereof to a predetermined value; and a voltage adjustment part serially connected to the constant current circuit part and adjusting a potential difference between the upstream and downstream sides with a switching regulator. This therefore permits providing an LED driver capable of, while adopting a constant current driving method using a constant current circuit, easily minimizing unnecessary power consumption and respecting the permitted loss at the constant current circuit.

Abstract: A phase comparator that is configured with a fewer number of gates in an ECL circuit configuration as compared to conventional phase comparator circuits. The phase comparator also operates with lower current consumption, and can achieve a suitable detection of small phase difference by substantially suppressing the influence of spike noises which may arise in the signals input to the phase comparator.