Patent ID: 8159285

Claim:
A current supply circuit comprising: an operational amplifier comprising first and second input terminals and an output terminal; a transistor comprising a control terminal electrically connected to the output terminal of the operational amplifier, and comprising first and second main terminals; a first resistance between the first input terminal of the operational amplifier and the first main terminal of the transistor; a second resistance between a predetermined node and a ground line, wherein the predetermined node is between the first input terminal of the operational amplifier and the first resistance; first to Nth transistors, each of which comprises a control terminal electrically connected to the control terminal or the second main terminal of the transistor, and comprises a main terminal configured to output a current, where N is an integer of two or larger; and first to Nth switching transistors, each of which comprises a main terminal, wherein the main terminals of the first to Nth switching transistors are respectively electrically connected to the main terminals of the first to Nth transistors, a control terminal of the respective first to Nth switching transistors configured to receive a pulse width of a signal, wherein the pulse width is set to be constant regardless of a pulse frequency of the signal.