Analog Devices, Inc. the world's number one supplier of amplifiers, announced the release of the AD855x and AD857x families of high performance, low-cost, auto-zero op amps for high-volume applications. Through extensive enhancements to proven design architectures, AD855x/AD857x are the world's most accurate 3V to 5V op amps. The enhancements also allow ADI to price them at half the cost of competitive parts.

"Analog Devices is setting the standard for high-performance op amps in the high-volume market, says Steve Sockolov, Analog Devices' director of precision amplifiers. "Until now, you couldn't get this level of accuracy at a reasonable high-volume price."

Earlier entrants to the low-cost auto-zero amplifier class compromised performance, forcing design engineers to worry over error budgets and spend additional design time compensating for for op amp performance issues. Their only alternative was to buy expensive chopper amplifiers, generally priced well beyond most high-volume cost constraints.

With greater than 20-bit accuracy, AD855x and AD857x offer uncompromised performance. Design engineers can easily meet error budgets and cost constraints, save design time and improve time-to-market.

The AD857x family creates an enabling technology for many dynamic measurement and control systems, robotics, dynamic weigh scales and other "moving" signal applications. They are the first auto-zero products for broadband applications.

Talk to most design engineers about including a chopper (auto-zero) amplifier in their designs and they will probably roll their eyes at you and mutter, "noise, recovery, price." Even recent choppers have been difficult to design in satisfactorily, and the recovery-time problems have been a circuit killer in some cases. These two parts from Analog cure most of the ills of choppers as well as bringing some technology to the party that is looking for applications, rather than fixing some current problems. The parts also mark a major business transition for Analog into high-precision, low-cost parts.

With the modified architecture of the AD855x (with x being 1, 2 or 4 for single, dual or quad) the noise spike typical of choppers is reduced by about 40 dB compared to other products and the recovery time is within 200 microseconds (compared to milliseconds for earlier parts.) All auto-zero amplifiers have no 1/f noise so they are well suited for extremely low frequency use but even with the AD855x's lower noise floor only the bandwidth needed for the application should be used.

The AD857x goes a stage further by using a spread-spectrum technique for the switching frequency. This digital technique removes the typical, visible, chopper noise spike and spreads the effects across the spectrum. The noise floor that is yielded is a little higher than the AD855x -- but still much lower than the competition -- and the end-result is to give a usable 1.5-MHz bandwidth, a complete breakthrough for a chopper. This will allow for completely new products in the dynamic measurement fields and in robotics, plus whatever designers' imaginations can come up with.