Evaluation of Null Method for Operational Amplifier ShortTime Testing This paper investigates the NULL method to apply for the mass production testing of the operational amplifier. The NULL method is widely used to measure the operational amplifier characteristics accurately at the laboratory level, but it takes relatively a long measurement time. Then, we have examined the operation of the NULL method circuit with simulations where the SPICE model provided by the vendor is used for the amplifier under test. Some experiments have been also performed to confirm the agreements to the simulation results. We have found that the proper selection of the compensation capacitor values in the NULL method circuit can lead to shorttime and stable testing, which would yield its applicability to the mass production testing.

Improvements in Biasing and Compensation of CMOS Opamps In this paper, we present modifications to the constantgm bias circuit and Millerlead compensation of operational amplifiers which eliminate or minimize some of their shortcomings. First, we demonstrate how parasitic pad capacitance can cause instability in the constantgm bias circuit, and show that the transconductance is constant only for specific bias conditions. Next, we suggest a new circuit topology that requires 75% less compensation capacitance to achieve stability. We also discuss problems with Millerlead compensation that arise from temperature, process, and load variations. Finally, we present a new biasing technique to correct these problems, and, through simulation, demonstrate a 40? improvement in phase margin over load current variations.