CONSTANT CURRENT CIRCUIT

PURPOSE:To obtain a stable constant current output by feeding negatively a partial output of a current mirror circuit back to a reference current source so that the Early's effect is compensated and the dependence on the power supply voltage is removed for the output current. CONSTITUTION:A tra...

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Bibliographic Details
Main Author ASAMI TAKAO
Format Patent
LanguageEnglish
Published 25.07.1988
Subjects
AMPLIFIERS
BASIC ELECTRONIC CIRCUITRY
CONTROLLING
ELECTRICITY
PHYSICS
REGULATING
SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
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Summary:PURPOSE:To obtain a stable constant current output by feeding negatively a partial output of a current mirror circuit back to a reference current source so that the Early's effect is compensated and the dependence on the power supply voltage is removed for the output current. CONSTITUTION:A transistor TRQ5 different from a TRQ4 is connected to a TRQ3 and a current mirror circuit is constituted out only of a set of the TRQ3 and Q4 but a set of the TRQ3 and Q5. Then the output current I0' of the TRQ5 is fed back to the emitter of a TRQ2. The TRQ3-5 are set laterally in a monolithic IC and therefore have the similar characteristics. When the power supply voltage V<+> has variance, the output currents I0 and I0' of the TRQ4 and Q5 are fluctuated with the I0/I0' ratio kept constant. Thus the value proportional to the level of the Earl's effect can be negatively fed back to a reference current source (TRQ2). In such a way, it is possible to compensate the Early's effect of the current I0 and to remove the dependence on the power supply voltage for the output current. Then a stable current output is obtained.
Bibliography:Application Number: JP19870011318