Fake ICs - UK Vintage Radio Repair and Restoration Discussion Forum

dinkydi · 2nd Feb 2013, 12:03 pm

I have opened this thread as a companion to the "Fake Transistors" thread.

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. There is little monetary incentive for counterfeiters to fake low-price ICs. However, higher-priced ICs are commonly targeted, particularly if there is a demand. The fakes are sold through non-authorised distributors (particularly anonymous online sellers). Here is an example of some op amps that I examined to determine authenticity.

The IC type was a high-performance Burr-Brown operational amplifier OPA2134, a dual amplifier in a plastic 8-pin DIP configuration. First the package was examined, then the electrical performance.

Some samples of the op amps are shown in the photos. The logo and lot trace code (LTC) generally follow the manufacturer's rules and all LTCs were the same. There is no end notch in the package which is unusual for Burr-Brown amps of this type. The pin-1 designator is unlikely in terms of size and position. On the bottom side the die mark is wrong - it should state the country of manufacture. 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. This corresponds with a wide variation in surface quality, as the photos show. The case molding finish is of poor quality. Overall the variability and poor quality of the case is incompatible with that of a major manufacturer.

A 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. With the positive input of the amp grounded and unity feedback, the offsets were measured with a meter. 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. The input devices were found to be FETs, as they should be. Another simple test is to measure the supply current. This was found to be 4.0mA average rather than the expected 8mA average.

Although no AC tests had been performed it was already certain that the op amps were counterfeit. (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.

Peter

2nd Feb 2013, 12:03 pm	#1
dinkydi Retired Dormant Member Join Date: Feb 2011 Location: Sydney, Australia Posts: 277	Fake ICs I have opened this thread as a companion to the "Fake Transistors" thread. 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. There is little monetary incentive for counterfeiters to fake low-price ICs. However, higher-priced ICs are commonly targeted, particularly if there is a demand. The fakes are sold through non-authorised distributors (particularly anonymous online sellers). Here is an example of some op amps that I examined to determine authenticity. The IC type was a high-performance Burr-Brown operational amplifier OPA2134, a dual amplifier in a plastic 8-pin DIP configuration. First the package was examined, then the electrical performance. Some samples of the op amps are shown in the photos. The logo and lot trace code (LTC) generally follow the manufacturer's rules and all LTCs were the same. There is no end notch in the package which is unusual for Burr-Brown amps of this type. The pin-1 designator is unlikely in terms of size and position. On the bottom side the die mark is wrong - it should state the country of manufacture. 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. This corresponds with a wide variation in surface quality, as the photos show. The case molding finish is of poor quality. Overall the variability and poor quality of the case is incompatible with that of a major manufacturer. A 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. With the positive input of the amp grounded and unity feedback, the offsets were measured with a meter. 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. The input devices were found to be FETs, as they should be. Another simple test is to measure the supply current. This was found to be 4.0mA average rather than the expected 8mA average. Although no AC tests had been performed it was already certain that the op amps were counterfeit. (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. Peter Attached Thumbnails