Temperature compensated current source
AssigneeTektronix, Inc.
InventorsMichael H. Metcalf, Stewart S. Taylor
Life of this patent
Estimating the term…
Abstract
A current source provides an output current whose magnitude is substantially independent of changes in temperature. In each of three embodiments (50, 100, 120), one or more bipolar transistors are employed to provide a compensating current which is dependent on the base-to-emitter voltages, V.sub.BE, of such bipolar transistors. The compensating current changes with temperature so as to offset changes in the uncompensated output current so that the total output current is substantially independent of V.sub.BE. The three embodiments employ current mirror circuits (10, 122) that provide a current source of simple circuit design that is operable with the use of a single power supply at a relatively low voltage.
Claims12
A temperature compensated current source, comprising:
- a current mirror circuit including first, second, and third transistors each having a base, a collector, and an emitter, the bases of the first and second transistors being coupled together and to the emitter of the third transistor, the emitters of the first and second transistors being coupled together and to a first source of reference voltage, the collector of the first transistor and the base of the third transistor being coupled together to form a current input, and the collector of the second transistor forming a current output;
- a reference impedance coupled between a second source of reference voltage and the current input for establishing an input current;
- and
- compensating current means for injecting a compensating current into the collector of the first transistor such that the output current flowing in the collector of the second transistor is substantially temperature invariant.
A temperature compensated current source, comprising:
- a current mirror circuit including first and second transistors each having a base, a collector, and an emitter, the bases of the first and second transistors being coupled together and to the collector of the first transistor to form a current input, the emitters of the first and second transistors being coupled together and to a first source of reference voltage, and the collector of the second transistor forming a current output;
- a reference impedance coupled between a second source of reference voltage and the current input for establishing an input current;
- and
- compensating current means for injecting a compensating current into the collector of the first transistor such that the output current flowing in the collector of the second transistor is substantially temperature invariant.
Dependencies are inferred from the claim text.