Design techniques for IC voltage regulators without p-n-p transistors

Design techniques for IC voltage regulators without p-n-p transistors are discussed. Included is a brief discussion of the problems associated with p-n-p transistors that can be used as shunt devices in voltage regulators, as well as two methods for eliminating the p-n-p shunt device that is commonly used in regulators. The first method applies to nontemperature-compensated voltage regulators. It is a method of reducing the sensitivity of regulators to changes in power supply, using a phi cancellation technique instead of a p-n-p shunt device. This method greatly improves regulator voltage tracking. The second method is a method of eliminating the p-n-p transistor in a temperature-compensated bandgap-referenced voltage regulator using a differential amplifier to maintain current equality in tracking transistors. It is shown that the elimination of the p-n-p device will add a higher degree of design freedom while decreasing the susceptibility of the design to process variations.