Temperature stabilized constant fraction voltage controlled current source

摘要

A current source includes a control stage responsive to a stable, d.c. input voltage that is operative to produce a control voltage proportional to absolute temperature (PTAT), and an output stage responsive to the PTAT control voltage that is operative to produce an output current that is an essentially constant fraction of an output constant current source. The control stage includes a temperature-dependent control resistor of a given resistor type, and at least one control constant current source providing the control resistor with a temperature dependent control current. The temperature dependent current source includes a temperature dependent current source resistor based on the given resistor type such that the temperature dependencies of the control current and the control resistor tend to cancel in such a manner that a true PTAT control voltage is developed. The output stage includes an output transistor coupled to an output constant current source such that an output current of the output stage has no current contribution other than from the output current source. A method for providing a current that is a constant fraction of an output constant current source includes the steps of: (a) developing a control current that is based on the same resistor type as a control resistor; (b) applying the control current to the control resistor to develop a control voltage that is proportional to absolute temperature; and (c) applying the control voltage to a current divider coupled to an output constant source to provide an output current.