acquisitionZONE Products for the week of September 10, 2007
Texas Instruments Says…
OPA369: Low Power Zero Crossover Op Amp for Battery-Powered Portables
Precision, 1 µA Amplifier Simplifies High-Performance Designs
Texas Instruments Incorporated (TI) introduced the industry's lowest power zero-crossover operational amplifier (op amp). Featuring a unique single-input-stage architecture, the OPA369 achieves rail-to-rail performance without input crossover to solve the common design problem of input offset distortion due to the change in common mode voltage that is very prominent in low-voltage, rail-to-rail applications. Combined with 1uA quiescent current, SC70 package and operation down to 1.8V, the OPA369 simplifies high-performance designs in battery-powered, portable products.
"The OPA369 utilizes TI's innovative zero-crossover topology and next-generation CMOS process technology to offer precision performance previously unavailable in 1uA single-supply amplifiers," said Art George, senior vice president of TI's high-performance analog business. "Typically, designers are forced to choose between power consumption and the AC or DC performance of their signal conditioning amplifiers. The OPA369 will enable customers to increase the precision in their portable applications without complicating the design or increasing their power budget."
This is quite a feat that TI is pulling off here! I almost wrote "trick" but there is no legerdemain here -- this is real.
Here we have a rail-to-rail input op amp with no perceivable crossover and, therefore, no crossover distortion. The input offset voltage is just flat right through the complete common-mode range. The actual number is a typical 250 µV with a maximum 750 µV. CMRR is a minimum 100 dB.
At the same time the part has not achieved this performance by throwing current at the problem. The per channel typical quiescent is just 0.7 µA over the supply rail range of 1.8 V to 5.5 V. The input bias and offset currents are both, typically, 10 pA.
Channel separation in the dual part, at 1 kHz, is a typical 120 dB (suggesting dual die) while open-loop voltage gain with 100 kΩ load, over temperature is a minium of 100 dB. This falls to 90 dB when the load is reduced to 10 kΩ.
The part is very nearly rail-to-rail at the output going within 10 mV of the rails with a 100 kΩ load and 25 mV with a 10 kΩ load.
Gain-Bandwidth product is a typical 12 kHz while the slew rate is 0.005 V/µs. The input voltage noise density at 1 kHz is a very decent 120 nV/rtHz.
The remarkable lack of crossover is a significant breakthrough and the parts can, obviously, because of the low quiescent, be dropped into any portable device in simple low-frequency or sensing applications. But that lack of crossover makes them a great choice for any number of precision medical sensor, or test and measurement applications and the price, for those applications, is a giveaway. These parts and, more significantly, this architecture are going to be big money spinners for TI.
The dual OPA2369 is in production in SOT-23-8 and MSOP-8 with pricing starting at $1.20 in 1000-piece lots. When in production the single OPA369 will be in SC-70-5 with no pricing yet announced.