Temperature and power supply stable current source

摘要

Current source circuitry consisting of a first n-channel field effect transistor (FET) and voltage generator circuitry coupled to the gate of the first FET. The voltage generator circuitry acts to control the current through the first FET such that it is essentially constant even with power supply, temperature, and many processing variations. The voltage generator circuitry consists of a second FET, a two input differential operational amplifier, a resistor, and an n-p-n transistor if the resistor has a positive temperature coefficient. A negative feedback path using the amplifier and the second FET ensures against current changes in the first and second FETs even if there are changes in one of the power supply levels and/or many semiconductor processing variations.