# The Signal

• #### 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...
• #### 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...
• #### 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...
• #### 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...
• #### 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...
• #### Taming the Oscillating Op Amp

Last week we looked at two very common reasons for oscillations or instability in op amp circuits. The ultimate cause of both was delay or phase shift in the feedback path. Review it here . I confess that I had intended to discuss cures for both circuits...
• #### 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...