21 2

Analog Devices Breaks New Ground For Vital Sign Detection And Portability In Patient Monitoring Medical Equipment

ADI’s new JFET-input in-amp improves performance and shrinks package size by 50%, increasing channel densities in patient monitors and portable medical electronics.

Analog Devices continues its history of serving the medical electronics industry by introducing the AD8220 JFET-input instrumentation amplifier. The AD8220 enhances the detection of patient vital signs in both fixed-line and transportable electrocardiograms (ECGs), electroencephalograms (EEGs) and other types of patient monitoring devices. Housed in an 8-lead plastic MSOP (mini-small-outline package) that is half the size of competing devices, 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. 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 ВµA, making it ideally suited for use in portable patient monitoring systems.

21 3

The AD8220 features an extremely low input bias current of just 4 pA (pico amps), which is less than half the level of competing components and addresses a significant source of signal error in precision instruments. 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. The high CMRR, meanwhile, shields these signals from outside interference by rejecting electrical noise from other parts of the human body.

About the AD8220
With JFET (junction field effect transistor) 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 ВµV/В°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 ideally 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 automation applications, such as electrometers and other precision instrumentation systems where extremely small currents must be measured in electrically noisy environments.