Today’s blog is about a new amplifier from Analog Devices. Amplifiers are pretty special to ADI since they were the first products we ever made, back in 1965. This is reflected in our company logo which features a tilted triangle - the schematic symbol for an amplifier:

ADI logo

Amplifiers are hugely important. Without them we simply could not have the modern world. Radio used to be nothing more than bursts of static which could travel only a few hundred miles, at best. Telegraph and telephone networks used electro-mechanical devices to relay signals, but there wasn’t much amplification. Then, in 1906, Lee de Forest invented what he called the Audion tube. It took six more years but by 1912 he had perfected the first fully electronic amplifier. By today’s standards it was noisy and didn’t amplify very much, but improvements came fast and furious. Over the next few years as tubes got better at amplification, they also got smaller.

RCA Nipper Dog

Before amplifiers, cones provided the amplification of sound from cylinder and disc players

In 1947 a team at Bell Labs developed the first working transistor. Not only was it way smaller than even the smallest tube, it barely generated any heat, because instead of a hot filament causing the flow of electrons, the transistor did it using a non-heating material called a semiconductor. That story is a whole blog in itself. For now, we’re going to focus on a special arrangement of about thirty to fifty transistors into a device called an operational amplifier, or op amp. At its most basic, an op amp schematic looks like this:

Basic Op Amp

Thanks to its easy configurability the op amp is one of the most widely used electronic components today. By adding a few resistors in the right places, the op amp can deliver varying levels of amplification. It can also be configured to output the sum or difference of two signals. It’s really quite an amazing, flexible device.

One of the jobs an op amp might have is to connect with a device, called a sensor. The sensor’s job is to detect signals (such as vibrations, voltage, sound, or light) and pass them to the amplifier. In this case the amplifier’s job is to amplify that signal and pass it along onto another device, called a converter. The converter then turns that real-world signal into the ones and zeros understood by the microprocessor. Some of those sensors are… well, sensitive. Attaching a regular op amp to the output of that sensor can actually cause the sensor to deliver false information. Which means for all their versatility and flexibility, an op amp is not right for every job.

Solving the problem is a new JFET (pronounced JAY-FET) op amp from Analog Devices, the ADA4625-2. JFET is short for junction gate field-effect transistor. What this means is the designer can connect the output of an ultra-sensitive sensor to the input leads of the ADA4625-2 and not worry about the original signal from the sensor getting corrupted. This op amp is also extremely low noise – among the lowest for any JFET amplifier in the world. Which means what gets passed along to the converter (and then to the processor, where complex analysis of the signal occurs) is a reliable, accurate copy of the original signal.

Even with all the work being done by the ADA4625-2 it is extremely power efficient, an important attribute with so many products being battery-powered these days. So is the very small package in which the op amp resides – or rather, op amps, plural. The “-2” at the end of the model number indicates two separate JFET amps sit inside this small IC. The ADA4625-2 can process two different signals at the same time, saving space for adding ICs and more features to the final product.

For details on the ADA4625-2, including the opportunity to download the datasheet or order free samples, we invite you to visit the ADA4625-2 product page today.

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