It is sometimes interesting to read how people buy expensive Opamps at eBay to very attractive prices. One IC that is sold often on eBay is the AD797. It is used a lot from people who want to “improve” their audio equipment. I will not discuss this here, why these “improvements” often make things worse, but look at the prices you pay on eBay. The retail price of a single AD797 chip at European retailers is >10$, but you find Chinese retailers on eBay that sell two of them for less than 6$. Looking at the price list from Analog, you will notice that this is even less than the price per IC you have to pay for 1000 units from Analog. How can this be? The answer is easy: fakes. Most of the buyers use these opamps in audio circuits. They never notice that it is a fake. Why? Because even the cheapest Opamps work great in audio circuits. Depending on the circuit, they might even perform better than expensive chips. The chip might not be an AD797, but it works well. So everybody is happy.

Fakes are one reason, why I would never buy parts like this on eBay. I’ve already seen fakes even for relatively inexpensive chips.

But today I found an interesting board:

 This is a switching voltage regulator based on the LM2596-ADJ. 5 boards are 4.81€ including shipping from China. Are you kidding me? The chip itself costs about 2-3 US$ when you buy it in large quantities. In small quantities it is about 5 US$. There is no chance to build 5 boards like this and ship it to Europe for under 5€. How can it be?

Some ideas:

• The chip itself is a fake or it is an old non-ROHS version that cannot be used anymore. But even with this, it will be really hard to build it cheap enough. The inductance on the board alone will cost at least 0.30-0.50 USD.
• The board itself was produced for something else and never used. Looking at the board this seems also relatively unlikely as this is a standalone PCB and input and output are designed to solder cables.
• This is an old evaluation module for this IC.

In 3-4 weeks these boards should arrive here and I will have a closer look. I will also order a sample from TI to find out if these chip on these boards look and behave different from genuine TI parts.

One final remark: Independent if these boards work well, I cannot recommend eBay to source electronic components. Ask yourself: Why should components from a 3rd party source be cheaper than from the supplier? The risk to buy fakes is very high. Sometimes suppliers have different qualities of the same chip design. Some guys buy the cheapest version and relabel it as the most expensive version.

PS: I will not post the eBay link.