# The Signal

• #### SPICEing Op Amp Stability

SPICE is a useful tool to help check for potential circuit stability problems. Here is one simple way to do it: Figure 1 shows a non-inverting amplifier using the OPA211 with a couple of minor variations that are common in many applications. R3-C1...
• #### Oh, That Interview Question— a reprise

After some Facebook chatter on last week’s blog , I think it deserves some follow-up. Here is the interview question that has bugged me for 41+ years: A 1V AC source is connected to a 1Ω resistor in series with a 1Ω reactance capacitor...
• #### SPICE It Up! … but does Bob Pease say no?

August 22, 2012 Anyone who has read a few of my blogs has seen that I simulate circuits in SPICE. You may know that Bob Pease was pretty opinionated about SPICE and once wrote, “SPICE takes away your ability to get good insights on what is happening...
• #### Resistor Puzzle—the sequel

It’s time for some fun! I’ve known a few folks who have tormented colleagues with a resistor cube—equal resistors on all sides. So in case you’ve solved that one, let’s add a twist. In this cube, not all the resistors are...
• #### PCB Layout Tricks—striped capacitors and more

I posed a question a couple of weeks ago regarding film capacitors—what’s the meaning of the stripe on one end? Check the picture below. These are non-polarized capacitors so it’s not a polarity marking. A reader, Richard, answered...
• #### Resistor Puzzle Solution... and a rant on schematics

Did you see last week’s resistor puzzle? Check it out if you missed it . Here’s the solution: We’re not accustomed to reading three-dimensional schematics so the first step is to redraw it clearly. There are three distinct paths from...
• #### Paralleling Op Amps—is it possible?

Is it possible to parallel two op amps to get twice the output current? We get this question periodically on our E2E forums. Though we may answer with a qualified “yes,” it tends to make us shudder just a bit. It can be done… but...
• #### Knowing Where to Tap

Jake, a respected veteran engineer in a power generation plant, retired with great congratulations and accolades. A few months later the plant suffered a major malfunction—a real meltdown with all systems involved. The engineering staff could not...
• #### Op Amps used as Comparators—is it okay?

Welcome to “The Signal,” a technical blog focusing on analog signal processing circuits . Op Amps used as Comparators—is it okay? Many of you (and I, too) occasionally use an op amp as a comparator. Often, this is when you only...
• #### Honoring an Analog Giant

Bob Pease died a year ago yesterday. What a loss for us analog heads who struggle to make our circuits work. His wealth of knowledge and experience seemed limitless. His insight and intuitive explanations helped so many engineers understand their circuits...