P-Channel MOSFET Tutorial with only Positive Voltages

From the mailbag (or chat… bag?)

Positive Voltages with a P-Channel MOSFET Tutorial

On every page of my blog, you might notice a chat window. If I’m not busy, we can chat in real-time. If not, the messages come to me by email. Here’s one I got from Matt the other day:

Let’s talk a bit about how (and why) you would use a P-Channel MOSFET. Matt, and he’s not the only one, is probably asking this question based on the “myth” that P-Channel MOSFETs require “negative voltage” supplies.

Keep reading for a how to use only positive voltage in this p-channel MOSFET tutorial.

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Can a 1µF decoupling capacitor be too much?

What happens when a breadboard Arduino skips a decoupling capacitor or two

1uF Decoupling Capacitor Circuit

To save time, breadboard pins or just lack of knowledge people try to skip adding eve one decoupling capacitor to a circuit. Either on IRC or in Forums you can almost always see it coming: “randomly, my circuit stops working” And then, “what do you mean a decoupling capacitor?” question.

While working on breadboard Arduino, I came across some unexpected measurements. Initially, the only capacitors on the breadboard were the two 22pF from crystal to ground and the capacitor connected to RESET for Auto-RESET.

Keep reading to find out what happen when I added a 100nF and a 1µF cap. A bunch of scope traces and surprising results follow.

Breadboard Arduino with no Decoupling Caps

Breadboard Arduino with no Decoupling Cap

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The_Spark_Gap

Karl and Corey run The Spark Gap Podcast which is focused on embedded electronics. On Episode 25 they interview me about Capacitors. We covered all the major types of caps, plus some application bits. Check out their show notes for an impressive array of links on the subject.

Also, my favorite episode of theirs so far is episode 18.  The guys talk about different serial protocols like SPI, I2C, CAN, etc.  Really good stuff.

Date: January 28, 2015
Appearance: Capacitor Questions Answered on The Spark Gap Podcast
Outlet: The Spark Gap Podcast
Format: Podcast

10818399_10152509408852219_5757913693783094151_oUnderstanding what X2 or Y1 capacitors actually are and are not is important when designing them into an AC-mains connected power supply.  Recently Electronic Products Magazine ran an article I wrote on the proper role of X and Y safety rated EMI Capacitors.

The X2 capacitor rating means different things to different people–except for UL.  When I wrote this article to discuss some common misconceptions around what X2 Rated Capacitors are, and how they can be properly used.

In case the PDF reader doesn’t load, it’s on Page 20 of the November 2014 issue.

You can see the full article with the EP Reader, by clicking here.

Date: November 1, 2014
Appearance: Role of EMI X1, X2, Y1, Y2 Capacitors Ratings
Outlet: Electronic Products Management
Format: Magazine

Article I wrote on some innovations KEMET has implemented in their capacitors:

There is no Moore’s Law for passive components like capacitors, but relentless development is delivering the kinds of devices engineers need to deliver cutting-edge new products for modern living. Capacitors have for many years enabled electronic designers to manage energy within circuits and fulfill basic functions like filtering noise or harmonics, correcting power factor, stabilizing feedback circuitry, coupling/decoupling, interfacing between voltage levels, and storing energy. But the demands placed on these components continue to increase, as electronic devices are expected to be smaller, longer lasting, more feature rich and more robust.

Read “Capacitor Innovations Address Emerging Opportunities” on Power Systems Design.

Date: December 30, 2014
Appearance: Capacitor innovations address emerging opportunities on PSD
Outlet: Power Systems Design
Format: Magazine

One of the best ways to describe a transistor is as an “electronic switch.”  They are solid state devices that make up almost everything in our world.  This video by Veritasium, which is a bit older, covers how n and p-type transistors actually work.

This complements the Addohms videos on BJTs and MOSFETs, which are more about how to use them.

If you’ve never watched a Veritasium video, do yourself a favor and set aside a few minutes. He’s like the Alton Brown of science.

The 4 best transistors to keep in your parts kit

When your project needs a transistor, there are tons of choices.  Which makes answering the question “Which transistor should I use or buy?” a daunting task.  Fear not, before wading through spec sheet after spec sheet, consider one of these four general purpose transistors.  Every electronics enginerd’s toolbox should have a few of each.

Transistors are one of the most versatile discrete components in electronics.  In digital circuits, they switch on and off while in analog circuits they are used to amplify signals.  For most projects, they are used to turn on a load that would kill the I/O pin of a microcontroller or microprocessor.   For most circuits either a BJT or MOSFET can be used, depending on the load current you need to switch.

[Edit Note]  Jan (comment below) points out that there are European Equivalents that may be more available for those located in that part of the world. For NPN Check out the BC547, for PNP the BC557.

Here are some more details on each of these.

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Electronics: Introduction to Breadboards

Soldering every circuit you build probably isn’t practical.  At some point you are probably going to want to use some type of temporary method to connect different components together.  One of the popular methods is using a breadboard.  This simple (and cool) looking device only needs a few instructions before you can begin

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Ouch. The Arduino GSM shield has a pretty serious design flaw, with its capacitors.

Tantalum is a really misunderstood capacitor. Well, all capacitors are misunderstood, but that’s a subject for another post. I ran across this post on the Arduino forums on the Arduino GSM shield. In the post, ddewaele, reports that the shield blew up, catching fire. At first some might think it was due to abuse by the user. While it is possible that reversing the polarity or applying over-voltage could cause a catastrophic failure, it is also possible that the user doing nothing wrong could result in the same failure mode!

Wait, what? So what gives? Well, there’s two things to understand. First, Tantalum doesn’t explode. It takes almost 2000°C before Tantalum metal will ignite. Okay, so if Tantalum doesn’t explode what is ddawaele seeing? It’s the cathode material, Manganese Dioxide, (MnO2) that is exploding…

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