Precision op amp tolerates signal overloads

November 07, 2014 // By Graham Prophet
Analog Devices claims the industry’s first and most robust operational amplifier that integrates input protection against signal excursions of 32V beyond the supply rails and 70-dB of rejection for electro-magnetic interference (EMI) above 1 GHz.

It is, ADI says, the first precision op amp with integrated input over-voltage protection and electro-magnetic interference filters for more robust solution with better accuracy. The ADA4177-2 dual-channel, precision, low-noise, low-input operational amplifier was designed to address system designers' needs for a sensor interface amplifier with precision, linearity and environmental immunity for mission critical process control, defence, aerospace and motor control applications as well as multi-channel data acquisition instrumentation designs.

The ADA4177-2 has a typical bandwidth of 3.5 MHz and 8-nV/√Hz voltage noise at 1 kHz while consuming 500 µA typical at 25°C with ±15-Vdc nominal power supplies. It is specified to operate in the -40°C to +125°C temperature range.

Low offset voltage: 60 µV maximum at 25°C

Low offset voltage drift: 0.7 µV/°C maximum

Low input bias current: 1.0 nA maximum at 25°C

Dual voltage supply operation:

Specified at ±5 V to ±15 V

Operation from ±2.5 V to ±18 V

In typical designs where an unprotected op amp is used at the front of the signal chain and exposed to energetic voltage and electromagnetic events, engineers often use external clamping and filtering techniques. These external components provide only limited effectiveness and often compromise the resulting system’s precision and accuracy over changes in temperature and common-mode voltage.

Using the ADA4177-2 at the front of the signal chain minimises the impact of these events by filtering out the EMI at the input to the op amp or limiting the in-rush current of an over-voltage event to a safe level. This reduces the need for external protection and filtering components, improving system accuracy and precision, reducing BOM cost and circuit board footprint while improving time-to-market. In addition, the ADA4177-2 op amp’s rail-to-rail output adds value for designers that need additional dynamic range. In SOIC-8 and MSOP-8 It costs $1.53 (1000).

A video is at; and a technical article at;

Analog Devices;