Temperature compensated constant-voltage circuit and temperature compensated constant-current circuit

摘要

A constant-voltage circuit which can be driven by a low voltage (lower than 1 V) of a nickel-cadmium battery, etc., and which provides a temperature-compensated stable voltage output. The constant- voltage circuit comprises battery 1, band-gap-type current-mirror-type constant- current source circuit 3 which outputs collector current I.sub. C9 of transistor Q.sub.9 with a positive temperature coefficient, current source circuit 5 which outputs collector current I.sub.C8 of transistor Q. sub.8 having a negative temperature coefficient and defined by base- emitter voltage V.sub.BEQ7 of transistor Q.sub.7, and a load resistor element R.sub.0. At node N.sub.0, collector current I.sub.C9 and collector current I.sub.C8 are added. The temperature coefficients of these two currents cancel each other. Consequently, the current at node N. sub.0 does not have temperature dependence. Load resistor element R.sub. 0 converts this current to a voltage as the output voltage V.sub.OUT.