I was thinking the other day about op-amps. I got a “New Product” email blast from a major analog IC supplier that discussed a few new op-amps. One was a “4MHz, 7nV/√Hz, Low Offset and Drift High Precision Amplifier.” Another was a “Low Power, 1 nV/√Hz, G≥10 Stable, Rail-to-Rail Output Amplifier” (single and dual versions available).
Packaged op-amps have been available since 1952 (if we go all the way back to the tube-based Philbrick K2-W). Monolithic op-amps date back to the μA709, vintage 1965. The '709 was a dog by most standards — external compensation, a tendency to latch up, and so forth — but it was a whole lot better than designing an op-amp from discrete transistors. It also used a lot less power than the K2-W, which needed a power supply to operate the tube filaments and positive and negative high-voltage supplies for the plate circuits.
In the 61 years since the K2-W, we've seen many enhancements:
- Internal compensation, starting with the μA741
- Process tricks like super-beta and circuit tricks like bias current compensation to reduce input currents
- More process tricks like adding JFET (and then MOSFET) input stages for lower event input current
- Laser, Zener zap, and chopper stabilization to lower offset voltage
- Faster processes to get more and more bandwidth
- Various tricks to lower distortion for high crest-factor signals
- Rail-to-rail inputs and outputs
- Lower noise, supply voltages, and power consumption
Today we can get singles, duals, quads, and octals, and a friendly vendor will put even more amps on a chip if you really want them. Of course, advances in packaging have shrunk op-amps to teeny weeny things, and prices have continued to drop.
There was a time when you had to choose between fast op-amps or precise op-amps. The newer generations offer both, so you don't have to choose in most applications. Some, of course, are optimized for either speed or accuracy.
And yet, with all these choices, new op-amps are still coming out. As of today, the TI website claims 1,381 different op-amps. Do we need them all? Do we really need any new ones?
I think that, if no new op-amps came out from TI, ADI, LTC, Maxim, or any other broadline analog IC house for the next few years, most designers would still be able to find something that met their needs. They would be able to get their circuits and systems designed and into production just fine.
But I'm curious if there are still any unmet needs out there. If you had your choice of one new op-amp that would solve your latest design problem, what would it be?