We all know that if you are going to look in the right place, you will find a large number of fake components, and the chip quotation on the auction website may be too good to be true. As a result, some marks may be erased to reveal something completely different. [imsai guy] saw a batch of cheap op-07 laser trimming operational amplifiers, so he picked them up for investigation. You can take a break by watching the video below.
When the two input voltages are the same, a perfect operational amplifier has a zero volt output, but in fact, no real device reaches this perfect level. It is called offset voltage. For instrument work with low offset voltage, some components, such as op-07, have been adjusted with laser to adjust their components to the lowest offset. This process is very expensive, so the real op-07 is also very natural.
In this case, it is very simple to identify the true operational amplifier and the false operational amplifier. Just connect the chip into a unit gain non inverting amplifier and measure the voltage on the output (we can’t help admiring Keithley 2015 thd multimeter!), The fake should be clear and visible through measurement. The first is some 741 with an offset > 1 MV (although the offset of the outlier 741 is 40) μ 5) , to show the expected function of low-cost operational amplifier, and then we saw op-07. When the offset is greater than 1.2 MV, we can immediately see that they are false, and as he admits, the price is not surprising. At the same time, we will pay close attention to the 741 made in Korea, such as outlier low offset equipment.
If you are interested in the internal structure of the operational amplifier, we suggest you take a look at the first integrated operational amplifier. At the same time, this is not the first fake chip we have seen.