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acquisitionZONE Products for the week of August 24, 2009
Intersil Says…
ISL28207: Low-Noise, High-Voltage pA Input Precision Operational Amplifiers
Created on Proprietary Precision Bipolar Process Technology ISL28207 Offers Top Performance for Instrumentation, Industrial and Data Acquisition Applications
Intersil Corporation, a world leader in the design and manufacture of high-performance analog and mixed-signal semiconductors, announced the ISL28207, the first in a family of operational amplifiers built using the company’s new proprietary bipolar process technology.
Intersil’s ISL28207 is a dual 40V low-power bipolar precision operational amplifier that exhibits outstanding DC precision and superb temperature drift performance. The device offers a low offset voltage of 75 micro-V max and a typical input bias current of 60pA. Temperature drift is only 0.65 micro-V/degree C max for input offset voltage and 0.2pA/degree C for input bias current, making it ideal for 16- and 24-bit applications. The ISL28207 exhibits a wide operating voltage range of 4.5V to 40V and an operating temperature range of -40 to +125 degrees C.
EN-Genius Says…
It is always refreshing to see a data sheet that offers specifications at two supply voltages, in this case at both ±15 V and ±5 V.
Over the full operating temperature (-40ºC to +125ºC) the maximum offset voltage for the single ISL28107 and dual ISL28207 is 140 µV with a rather incredible 0.65 µV/ºC drift. Input bias current is a maximum of 300 pA out to 85ºC and 850 pA out to the full +125ºC with a drift of just 0.2 pA/ºC. The input voltage range is within 2 V of each rail with a little more available on the output. Open-loop gain is a typical 50,000 V/mV while the slew rate is a typical ±0.32 V/µs and gain-bandwidth product is just 1 MHz.
Input voltage noise density is disappointing. Quoted only with ±19 V rails it is about 13 nV/rtHz typical from 10 Hz to 10 kHz, showing low 1/f characteristics.
Typical supply current per channel is 210 µA and crosstalk between channels in the dual part is fairly level at 130 dB (another positive crosstalk number in a data sheet!) out to about 8 kHz and it then falls rapidly to about 20 dB at 5 MHz.
It is interesting to see a new process that pushes the high-end supply voltage to 40 V. The lowest supply that can be used, at 4.5 V, is not going to be optimal for a lot of designers. The low input bias current and low input offset are very attractive, but the input noise is not “very low” as stated on the data sheet (when did descriptors like that deserve a place on a technical document?) and using the op amps with 16-bit and 24-bit ADCs – as promoted in the news release – is just not going to happen in applications where a designer knows how to use all that resolution. Where the input bias current drift is important, particularly in medical instrumentation, the extra money being requested for these op amps will not be a problem. They will do well because of that. Will they do outstandingly well? Intersil still needs to establish itself as a supplier of op amps and it has to overcome the negatives of a few years ago when stories were rife that delivered devices were clearly not matching data sheet numbers. To get such new lines of op amp going, and we are told there are many more to come, the street price for a single is probably going to have to hit ninety cents.
The ISL28107 and ISL28207 are in production in SOIC-8 with pricing starting at $1.58 in 1000-piece lots.
Data Sheet
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