A Guide to Op Amp Selection

Operational amplifiers, more commonly known as op amps, have been a fundamental component in electronic designs for decades, and it’s easy to see why. With only a few changes in external components, a simple op amp can become an amplifier, a filter, an oscillator and even more.

Like many things in engineering, selecting an op amp comes down to compromises. Most of an op amp’s parameters are simply measurements of how much it deviates from the ideal model. For a simple amplification, you may be mostly concerned with finding the right supply voltage and output capability. For something involving precise measurements, offset voltage and bias current may be critical to reduce error. Defining usable ranges for these values is key to finding parts using the DigiKey search.

At the time of this writing, DigiKey has around 12,000 unique parts in the op amp family. Sorting through all of these using the filters can be daunting, but a bit of cleverness in the selection order can make it easier.

As with all my DigiKey searches, I like to start with the Packaging and Part Status parameters to remove all of the large quantity part number variants and select only active, stocking parts.

My next step is to start with high level parameters and work toward the lower level details. For example:

• High Level
• Mounting Type
• Output Type
• Number of Circuits
• Ratings
• Operating Voltage
• Output Current
• Application Details
For these specifications, selecting the range of acceptable values will give better results than trying to focus on a single value.
• Bandwidth
• Offset Voltage
• Bias Current
• Supply Current

I try to save parameters like Amplifier Type, Operating Temperature, and Package/Case until the very end. Since these parameters are very specific, it is easy to unintentionally exclude options that may have worked and remove good results from the search.

A more detailed breakdown of op amp specifications with basic example circuits can be found on the EEWiki. If you have questions, feel free to reach out to us through the TechForum.