Norwood, Mass. Analog Devices Inc. said it's breaking ground with its first junction field effect transistor-input instrumentation amplifier, which is the smallest in the industry and offers the highest common mode rejection ratio.
The JEFT input instrumentation amplifier is also said to enhance patient vital sign detection in both fixed-line and transportable electrocardiograms (ECGs), electroencephalograms (EEGs) and other types of patient monitoring devices.
Housed in an 8-lead plastic MSOP, the AD8220 in-amp allows designers of medical equipment to break new ground by freeing up additional board space to significantly increase ECG and EEG channel density, allowing for smaller medical monitoring systems, said Lew Counts, vice president, Advanced Linear Products at Analog Devices.
Monitoring equipment with high channel density also gives medical professionals more measurement points for very small signals like heart pulses and brain activity while protecting patient vital signs from electrical interference. In addition, the AD8220 operates on a single low-voltage power supply that draws only 700 μA, making it suited for use in portable patient monitoring systems.
The AD8220 features an extremely low input bias current of just 4 pA, which is less than half the level of competing components and addresses a significant source of signal error in precision instruments, Counts said. The AD8220 also achieves an 80 dB common mode rejection ratio (CMRR) up to 10 kHz (G=1), while competing in-amps guarantee only 72 dB to 200 Hz.
With significantly lower input bias current and higher CMRR, health care professionals can now measure heart pulses, electrical brain waves, and other patient vital signs at previously undetectable levels, Counts said. The high CMRR, meanwhile, shields these signals from outside interference by rejecting electrical noise from other parts of the human body.
With JFET inputs, the AD8220 in-amp achieves a guaranteed input bias current of 20 pA, maximum, and 4 pA, typical. It specifies a 1-nA input bias current over temperature, and 2 μV/°C input offset voltage temperature drift. The rail-to-rail output of the AD8220 allows designers to improve dynamic range by increasing the gain further before reaching the supply rails. Furthermore, the AD8220’s 80 dB CMRR (G=1) over frequency ensures that only the desired signals are monitored and unwanted common-mode signals are rejected.
The AD8220 is suited for patient monitoring systems, where its small size, low current noise and low input bias current increase the sensitivity and noise rejection of fixed-line and portable medical equipment, such as ECG and EEG systems. The low input bias and high CMRR characteristics also make the AD8220 a fit for industrial automotation applications, such as electrometers and other precision instrumentation systems where extremely small currents must be measured in electrically noisy environments.
The AD8220 is currently sampling, with production planned for November. The AD8220 is priced at $2.29 per unit, in 1,000-piece quantities. Click here for the AD8220 data sheet.
Analog Devices, 1-800-262-5643, www.Analog.com.
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