May. 25th, 2017

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I got an email hint today reading "The LM741 is useful for many beginner circuits but if you are having a lot of trouble getting it to behave try upgrading to a more modern TL072." This makes sense, as far as it goes, but the 741 dates from 49 years ago, and the TL072 is only slightly more modern, introduced 42 years ago.

These parts are known as "op-amps", short for "operational amplifiers". The concept has been around for even longer than these parts, and is an integral* part of a wide variety of circuits, even today.

It is true that the (slightly) newer TL072 is better in pretty much every aspect than the 741, which was one of the early single-chip implementations, and had fairly poor performance in most categories. However, for many years, it was good enough, and well-known enough that many manufacturers offered it, it was made in enormous quantities, and was dirt cheap.

For a while, people would use the cheap ubiquitous 741 wherever it would do, and the nicer and more expensive TL072 where the better specs were required. Later, the TL072 was the go-to chip, and the more expensive 5532 (1977) would be used where a better chip was required.

Time continued to march on, and now the 5532 is cheaper than the older TL072, and a good choice for whenever you need an op-amp. It's overkill for a lot of uses, but these days it's cheap and ubiquitous. The audiophile crowd pooh-poohs it, and likes to swap in fancier chips to get the sonic character they want.

However, in moderate bandwidth analogue electronics, things are simply not obsoleted as rapidly as they are in the digital arena. All of the chips I mentioned are still made, and easily obtainable. There are, of course, more modern chips out there. Overlooking the bewildering variety of special-purpose chips, there are some newer general purpose op-amps to be had. The OPA627 came out in 1989 (a mere 28 years back), and has some truly impressive specifications. However, it costs nearly fifty times as much money as a 5532. The AD823 appeared in 1995 and is a fine chip, and more affordable than the OPA627. However, perhaps you want to use a chip introduced in this century for some reason. And sure enough, a successor to the OPA627, the OPA827 was introduced in 2006, only 11 years ago.

* pun intended: one common use for an op-amp is a lash-up known as an "integrator"

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