power supply sequencing for opamps

11090flow power supply sequencing for opamps Most designers know that many prob- lems may arise between the paper design and the practical realization of that design. We are, of course, no exception, and one incident that we experienced recently illustrates a prob- lem that is of interest to pass on. Measurements were being carried out on a circuit that contained some type NE 5532 opamps which were powered from a ±12 V symmetrical supply. When the circuit was switched on, it did not function correctly. Measuring the supply lines revealed that the positive supply was —0.6 V instead of +12 V. When the +12 V line only was switched off and immediately on again, the malfunction disappeared. Switching off the mains and immedi- ately on again made the defect reap- pear. Using new opamps made no difference. After some research in relevant literature, it appeared that on switching symmetrical power supplies temporary polarity reversal may occur. Because of the complex internal structure...