Zener regulator in butted guard band CMOS

摘要

Butted guard band CMOS circuits have a typical breakdown of about 7 volts. It is often desirable to operate circuitry from supplies greater than 7 volts. For example, 9 volts is a commonly used supply value. An isolated zener diode is fabricated into a CMOS integrated circuit so as to develop a voltage drop equal to guard band breakdown. The zener voltage is coupled by way of a diode-connected transistor to the operating circuitry. The diode drop substracts from the zener voltage so that the circuitry is always operated at a voltage below its breakdown.