Patent ID: 7268528
Filing Date: 2007-09-11
Classification: G05F,H03F

Abstract:
1. A constant-current circuit that generates a plurality of constant currents and outputs the generated constant currents, comprising: a first transistor that generates a current corresponding to a signal input to a control electrode and outputs the generated current; a first pn junction element to which the current output from the first transistor is supplied; a second transistor that generates a current corresponding to a signal input to a control electrode and outputs the generated current; a first series circuit in which a first resistor and a second pn junction element are connected in series and to which the current output from the second transistor is supplied; a control circuit that controls the operation of the first and the second transistors so that a voltage of a connection point of the second transistor with the first resistor is equal to that of a connection point of the first transistor with the first pn junction element; and a proportional current generating circuit that generates a plurality of currents the currents being proportional to a current flowing in the first resistor; wherein the first resistor is connected to a potential difference generated by a difference of current densities flowing in the first and the second pn junction elements, the proportional current generating circuit consists of a plurality of transistors for generating proportional current to whose control electrodes a control signal output from the control circuit to the second transistor is input, and a current proportional to a current flowing in the first resistor is generated in each of the transistors for generating proportional current and the generated current is output.