ADI AD8244BRMZ-R7

The AD8244 is a precision, low-power, FET-input, quad, unity-gain buffer designed to isolate very high source impedances from the rest of the signal chain. With a maximum bias current of 2 pA, near-zero current noise, and an input impedance of 10 TΩ, it introduces virtually no error even with source impedances in the MΩ range. The AD8244's unique pinout addresses guard trace routing by physically isolating the high-impedance inputs from the low-impedance supplies and the outputs of other buffers. This configuration simplifies guarding while reducing board space, enabling both high performance and high density within the same design. The AD8244 is specifically designed to address buffer-related challenges. Its tight channel-to-channel matching allows the AD8244's channels to be used in differential signal chains with minimal error. The device features low voltage noise, a wide supply range, and high accuracy, making it versatile enough to deliver high performance in any application requiring a unity-gain buffer — even with low source resistances. The AD8244 is rated for the -40°C to +85°C industrial temperature range and is available in a 10-lead MSOP package.

The AD8244 is a precision, quad, FET-input, unity-gain buffer designed to isolate very high source impedances from the rest of the signal chain. N-channel JFETs are used as input transistors to provide a low offset (350 μV maximum), low noise (13 nV/√Hz typical), high-impedance (10 TΩ and above) input stage that can operate down to the negative supply voltage. Using a novel drift-trimming technique, the Grade B AD8244 achieves a very low offset voltage (0.545 mV maximum over the full temperature range), introducing minimal system error over the full temperature range. The AD8244 is optimized for high-precision applications such as buffering biopotential electrodes, where buffers must have tightly matched, ultra-high-impedance inputs and channels. A conventional quad op amp requires a minimum of 14 pins, whereas the AD8244 uses a 10-lead package, reducing routing space and eliminating parasitic effects from feedback traces. Furthermore, the flexible design and high channel density make the AD8244 well-suited for signal chains requiring unity-gain buffers.

• Low power supply current per amplifier: 250 μA (max)
• FET input bias current: 2 pA (max, 25°C), ultra-high input impedance
• Low noise voltage noise: 13 nV/√Hz (at 1 kHz)
• Voltage noise: 0.4 μV p-p (0.1 Hz to 10 Hz)
• Current noise: 0.8 fA/√Hz (at 1 kHz)

• Biopotential electrodes
• Medical instrumentation
• High-impedance sensor signal conditioning
• Filters
• Photodiode amplifiers