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#BURR BROWN OP AMP OFFSET MEASUREMENT PDF#
Google Patents Nanovolt amplifier designĭownload PDF Info Publication number US9077301B2 US9077301B2 US13/906,051 US201313906051A US9077301B2 US 9077301 B2 US9077301 B2 US 9077301B2 US 201313906051 A US201313906051 A US 201313906051A US 9077301 B2 US9077301 B2 US 9077301B2 Authority US United States Prior art keywords circuit input mos electrically coupled voltage Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. (If one has an authentic IC sample available for comparison, simple tests with an analog ohmmeter could also have been revealing.) The test results were consistent with the op amps actually being inexpensive TL082 or similar types.- Google Patents US9077301B2 - Nanovolt amplifier design This was found to be 4.0mA average rather than the expected 8mA average.Īlthough no AC tests had been performed it was already certain that the op amps were counterfeit. Another simple test is to measure the supply current. The input devices were found to be FETs, as they should be. The average offset was 4.0mV and the maximum 6.5mV! By placing a large resistor (10Mohm) in the feedback path any output variation shows that the input devices are BJTs rather than FETs. With the positive input of the amp grounded and unity feedback, the offsets were measured with a meter. Overall the variability and poor quality of the case is incompatible with that of a major manufacturer.Ī genuine OPA2134 has a maximum offset of only 2mV! The measurement of this parameter therefore seemed an easy way to test the op amp's credentials. The case molding finish is of poor quality. This corresponds with a wide variation in surface quality, as the photos show. In addition, each op amp has a different die mark indicating the use of many dies - a high production part, but such a mix with the same LTC is unlikely. On the bottom side the die mark is wrong - it should state the country of manufacture. The pin-1 designator is unlikely in terms of size and position. There is no end notch in the package which is unusual for Burr-Brown amps of this type.
#BURR BROWN OP AMP OFFSET MEASUREMENT CODE#
The logo and lot trace code (LTC) generally follow the manufacturer's rules and all LTCs were the same. Some samples of the op amps are shown in the photos. First the package was examined, then the electrical performance. The IC type was a high-performance Burr-Brown operational amplifier OPA2134, a dual amplifier in a plastic 8-pin DIP configuration. Here is an example of some op amps that I examined to determine authenticity. The fakes are sold through non-authorised distributors (particularly anonymous online sellers). However, higher-priced ICs are commonly targeted, particularly if there is a demand. There is little monetary incentive for counterfeiters to fake low-price ICs. Many of us buy integrated circuits (ICs) online (or from other uncertain sources) and it is up to us to determine if they are genuine. I have opened this thread as a companion to the "Fake Transistors" thread.
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