Integrated circuit with precision current source

摘要

An integrated circuit with precision current source includes a first MOSFET, a second MOSFET, an op-amp and a resistor formed on a common semiconductor substrate. The first MOSFET is characterized by a first multiplier (×M1) and the second MOSFET is characterized by a second multiplier (×M2) where a ratio of ×M2 to ×M1 is greater than one. An inverting input of the op-amp is coupled to a drain of the first MOSFET and an output of the op-amp is coupled to a gate of the first MOSFET. A negative feedback circuit limits a rise in output current under low output voltage conditions.

主权项

1. An integrated circuit with precision current source comprising:
a first metal-oxide semiconductor field-effect transistor (MOSFET) formed on a semiconductor substrate and having a first source, a first drain, and a first gate, wherein the first MOSFET is characterized by a first multiplier (×M1); a second MOSFET formed on the semiconductor substrate and having a second source, a second drain, and a second gate, wherein the second MOSFET is characterized by a second multiplier (×M2), and wherein a ratio of ×M2 to ×M1 is greater than one; an operational amplifier (op-amp) formed on the semiconductor substrate having a plus input, a minus input and an output, wherein the output of the op-amp is coupled to the first gate; a first resistor coupling the first gate to the second gate; a first current source coupling the plus input of the op-amp to a positive voltage supply; a second current source coupling the gate of the second MOSFET to ground; and a negative feedback circuit coupled to the second gate to limit an output current flowing through the second MOSFET.