Updated 8-MHz JFET op-amps resist EMI from switching transients

August 07, 2017 // By Graham Prophet
Analog Devices (ADI) has recently posted details of its ADA4622-1/ADA4622-2/ADA4622-4, which are a “next generation” development of the AD820/AD822/AD824 single-supply, rail-to-rail output (RRO), precision junction field effect transistors (JFET) input op amps. They are 30-V, 8-MHz gain-bandwidth, quad-packaged devices.

The latest version , ADI says, include improvements that make them desirable as upgrades without compromising the flexibility and ease of use of the existing range. For example, their input voltage range includes the negative supply and the output swings rail-to-rail; and input EMI filters increase the signal robustness in the face of closely located switching noise sources.


The speed, in terms of bandwidth and slew rate, increases along with a strong output drive to improve settling time performance and enables the devices to drive the inputs of modern single-ended, successive approximation register (SAR) analogue-to-digital converters.


Voltage noise is reduced; although the supply current remains the same as the AD820/AD822/AD824, broadband noise is reduced by 25%, and 1/f is reduced by 50%. DC precision in the ADA4622-1/ADA4622-2/ADA4622-4 improved from the AD820/AD822/AD824 with half the offset and a maximum thermal drift specification added to the ADA4622-1/ADA4622-2/ADA4622-4. The common-mode rejection ratio (CMRR) is improved to make the later devices more suitable when used in non-inverting gain and difference amplifier configurations.


The ADA4622-1/ADA4622-2/ADA4622-4 are specified for operation over the extended industrial temperature range of −40°C to +125°C, and operate from 5V to 30V, with specifications at +5V, ±5V, and ±15V. The ADA4622-1 is available in a 5-lead SOT-23 package and an 8-lead LFCSP package. The ADA4622-2 is available in an 8-lead SOIC package, an 8-lead MSOP package, and an 8-lead LFCSP package. The ADA4622-4 is available in a 14-lead SOIC and a 16-lead, 4 × 4 mm LFCSP.


They will be useful, ADI suggests, in configurations such as; high output impedance sensor interfaces; photodiode sensor interfaces; transimpedance amplifiers; as ADC drivers; and to build precision filters and signal conditioners. Medical and healthcare products are a particular area of focus, and ADI anticipates uses in clinical monitoring, health, wellness and fitness, ECG patient monitoring, non-invasive blood pressure measurement based on ECG and PPG [photoplethysmography, or optical transcutaneous blood flow measurement], sports watches and other wearable health monitoring.


Analog Devices; http://www.analog.com/en/products/amplifiers/operational-amplifiers/jfet-input-amplifiers/ada4622-4


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