1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, and more particularly, to a bandgap voltage reference circuit for providing a constant reference voltage in a semiconductor integrated circuit.
2. Description of the Related Art
Bandgap voltage reference circuits are used in semiconductor integrated circuits to generate a constant reference voltage. In a semiconductor integrated circuit using a bandgap voltage reference circuit, the accuracy of operation of the semiconductor integrated circuit depends on the ability of the bandgap voltage reference circuit to provide a constant reference voltage. Thus, the bandgap voltage reference circuit is required to stably generate a constant reference voltage. There are several factors which can cause fluctuations of a reference voltage output from the bandgap voltage reference circuit. For example, variations in temperature is a common factor.
The above information is widely known to those skilled in the art, and a conventional CMOS bandgap voltage reference circuit providing a constant reference voltage without being affected by temperature variation has been disclosed in "CMOS Analog Circuit Design" by Allen/Holberg, at pages 596-599. Another conventional CMOS bandgap voltage reference circuit has been disclosed in U.S. Pat. No. 4,588,941 patented to D. A. KERTH on May 13, 1986.
However, in conventional bandgap voltage reference circuits, a reference voltage can fluctuate with variations in a power supply voltage and in a manufacturing process of semiconductor integrated circuits.