acquisitionZONE Products for the week of November 22, 2004
Analog Devices, Inc., a global leader in high-performance semiconductors for signal-processing applications and the world's leading supplier of amplifiers, introduced a new precision, high-voltage CMOS amplifier that is 70 percent smaller than competing devices, using Analog Devices' new iCMOS industrial process technology. The AD8661 is a precision rail-to-rail operational amplifier that combines dual-supply, high-voltage operation with low offset voltage, low noise and low bias current. Using the added cost-efficiencies of its patented DigiTrim trimming process, the AD8661 is available at a highly competitive price point.
The AD8661 is ideal for industrial and instrumentation applications, such as process control, motor control, power-line filtering, point-of-load sensing, and amplification for pressure, strain, and temperature, that require a wide dynamic operating voltage range. Designed for both single- and dual-supply operation, it is also is well-suited for medical equipment, communications infrastructure, automotive and consumer audio applications.
"With the introduction of the AD8661, Analog Devices is addressing
the need of high-voltage electronics equipment with a standard rail-to-rail
device capable of accuracy and high performance," said Steve Sockolov,
product line director for precision amplifiers, Analog Devices, Inc. "While
other op amps may claim to support higher voltage levels, none have the
ability to combine dual-supply, high-voltage operation with the low noise,
low offset voltage, low voltage drift, high bandwidth, small package size
and competitive price point of the AD8661."
analogZONE Says . . .
This is one of the first products to come from ADI in their new iCMOS process, which is a modular one with high-voltage, CMOS and bipolar features, allowing for some interesting medium-voltage devices to be thought about, and developed.
Seeing an industrial op amp -- what this has to be called -- with a 4-MHz GBP makes me show my age because I immediately think of National's LF411, a very early JFET input op amp which wouldn't wake up until it had 10 V across it. It was later copied by both TI and (now) On Semi, both improving the performances and lowering the price but the original is still in production -- and you can even get it in TO-5, if you're willing to pay $4.95 in 1000s!
But beyond GBW product there is little to compare. All the numbers of the AD8661 -- and its dual and quad siblings -- save one, are better than the LF411; that exception is interesting because it is the slew rate and it may indicate some of the limitations of this modular process. The LM411 slew rate was 15 V/µs while the AD8661 is specified at a typical 3 V/µs. What is really interesting is that the power consumption per channel of the AD8661 is identical to that of the LF411 at 1.8 mA maximum.
The input performances are incomparable, however, with the AD8661 family showing an offset of 75 µV, an input bias current of a typical 0.3 pA and an input offset of 0.2 pA. The output of the family is also rail-to-rail with the high within 150 mV (with a single +5-V rail) and the low within 60 mV of ground. The data sheet also offers the specifications for split ±8.0 V rails. It would be nice to see the product also characterized with a single +12-V rail.
The family can sink or source 19 mA per channel and the PSRR is a whacking 95 dB, as is the CMRR: with the common-mode voltage between 0.1 V and 3.0 V. Noise is quite high at 12 nV/rtHz at 1 kHz but the headroom more than makes that irrelevant.
This family will do extremely well in industrial applications -- particularly control and sensing -- consumer audio, and other higher-voltage applications where noise headroom is being sought. The input characteristics suggest applications in photodiode work which you can think of as a high-impedance sensor source. I don't care for the premature release for a trade show -- but that's the analog in me.
The single AD8661 is sampling, with production in April 2005, in SO-8 and LFCSP-8 priced at $0.78 in 1000-piece lots. The dual AD8662 will be available in SO-8 and MSOP-8, and the quad AD8664 will be in TSSOP-14 and SO-14. Neither has been priced for publication.