标签: transistor

Several weeks ago I was meandering my way around my office building when I ran across my chums Ivan and Darryl playing with a new toy that Darryl had picked up on eBay.   This little rascal (the toy, not Darryl) turned out to be a component tester. I have to say that I was pretty amazed by what I saw; so much so, in fact, that I raced back to my office to purchase one of my very own.   First, I placed an order for the model Darryl and Ivan were playing with -- a Mega328 ESR Transistor Resistor Diode Capacitor Mosfet Tester w/ Test hook -- which is a mega-bargain at only $15.98 USD ($0 shipping and handling):   Mega328 ESR Transistor Resistor Diode Capacitor Mosfet Tester w/ Test hook (Source: Max Maxfield)   It turns out that there are a bunch of these things. For example, while I was rooting around on eBay, I also ran across this All-in-1 Component Tester Transistor Diode Capacitance ESR Meter Inductance (they really could work on the naming of these little scamps) for only $19.33 USD (again, $0 shipping and handling).   All-in-1 Component Tester Transistor Diode Capacitance ESR Meter Inductance (Source: Max Maxfield)   It does take a couple of weeks for these little ragamuffins to wend their way from China, but I really wasn't in too much of a hurry. They both arrived a few days ago and I just now found a few minutes to take them for a spin.   A few thought off the top of my head are that the $15.98 unit is incredibly reasonably priced and I do like the fact that it comes with the three flying test leads. On the down-side, it was poorly packed, the display was loose, and it doesn’t have an "Off" button, which means that after you've pressed the "Test" button and seen the results, you have to wait for it to turn itself off automatically.   By comparison, the $19.33 unit is more "rugged" and was much better packed. It also has an "Off" button, which is jolly useful if you want to test a bunch of components. This unit didn't come with any test leads, but overall I have to say that it's my favorite.   Next, I gathered a few components together -- a resistor, a couple of capacitors, a FET, and a relay (inductor) -- whatever I found lying around, really. Both of the units come with ZIF (zero insertion force) sockets. You plug the leads from your component into the ZIF socket (it doesn’t seem to matter which pins go in which holes), close the socket, press the "Test" button, and observe the results on the display. The image below shows the test of a 10µF ceramic capacitor.   Testing a 10µF ceramic capacitor (Source: Max Maxfield)   To be honest, these testers would be worth the money if all they did was test capacitors. I can’t tell you how many of these components I have lying around that I couldn’t use (until now) because I couldn’t read their markings. The fact that these testers also work with resistors and inductors and diodes and transistors is just cream in the cake, as far as I'm concerned.   Check out this video showing the $19.33 unit in action:   One thing that did impress me is the fact that, when I tested my FET, it appears (from the diagram presented on the display) that the tester correctly identified the fact that there's an internal protection diode. I know there is such a diode because that was one of my selection criteria when I purchased these transistors (I'm going to use them to control the meters in my Inamorata Prognostication Engine and the relays in my Nixie Tube Clock, so I need to protect myself from the effects of back-EMF).   On the other hand, it may be that this diode is just part of the FET diagram they used -- I need to try this with a FET I know not to have this diode to make sure.   The only area I think these testers could use some work is the way in which they number the component pins on the display and associate these numbers with the pins in the ZIF socket -- sometimes the mapping is obvious; other times less so -- but overall I feel this is a minor niggle and I think either of these units would complement anyone's workspace and/or make a perfect gift.

I was just meandering my way around the Adafruit.com website -- as you do -- when I stumbled upon something that made me gasp with awe and admiration (I'm just thankful I didn’t squeal with delight).   This is such a cool idea -- it's a XL741 Discrete Op-Amp Kit from those little scamps at the Evil Mad Scientist Labs. As it says on the Adafruit website: "This is a faithful and functional transistor-scale replica of the µA741 op-amp integrated circuit, the classic and ubiquitous analog workhorse."       In fact, this is an implementation of the "equivalent circuit" from the original Fairchild µA741 datasheet. It comes with terminal posts and solder points so that you can actually connect to it and build up classic and functional op-amp circuits.   But wait, there's more, because I then ran across this Discrete 555 Timer Kit , which also comes from the little rapscallions at the Evil Mad Scientist Labs. In this case, we're talking about a functional transistor-scale replica of the classic NE555 timer integrated circuit, which the Adafruit website correctly describes as "One of the most classic, popular, and all-around useful chips of all time."     I am completely blown away. I think this is a wonderful idea. I only wish I'd thought of doing something like this myself. In addition to being great to play with oneself, these kits provide an absolutely brilliant tool for teaching basic principles to newcomers to electronics. Now I think I want to learn more about those little rascals at the Evil Mad Scientist Labs...

I think I may have "over-indulged" several days ago whilst watching the Super Bowl. I was certainly "relaxed and refreshed and feeling no pain," as it were. The problem is that things all seem to be a little "fluffy" around the edges the morning after. I'm finding it a tad difficult to get my brain to go into gear – it's like trying to fire-up a car that doesn't want to start – you keep on turning the key and the engine sort of splutters into life – and then it judders to a graunching halt again. This might explain why I'm having so much difficulty wrapping my brain around a question that came winging its way across the Internet to me that day. But first, let's set the scene. In Chapter 6 of my book Bebop to the Boolean Boogie: An Unconventional Guide to Electronics (still the only electronics book in the world to include a Seafood Gumbo recipe) we consider how to construct primitive logic gates using CMOS technology (PMOS and NMOS transistors connected together in a complementary manner).   We start off with a simple inverter function in the form of a NOT (or INV) gate as shown below. If input 'a' is presented with a logic 0 (for example, if we used a wire to connect it to the VSS line), then NMOS transistor Tr2 will be turned Off, PMOS transistor Tr1 will be turned On, and output 'y' will be connected to VDD (logic 1) via Tr1.   Similarly, if input 'a' is presented with a logic 1 (for example, if we used a wire to connect it to the VDD line), then PMOS transistor Tr1 will be turned Off, NMOS transistor Tr2 will be turned On, and output 'y' will be connected to VSS (logic 0) via Tr2. I then go on to explain that a non-inverting BUF (buffer) gate is more complex than a NOT gate. This is due to the fact that a BUF gate is essentially constructed from two NOT gates connected in series as shown below:   So far, so good. But now we move to consider the email I received, which reads as follows: Respected sir, I read your book "Bebop to the Boolean Boogie" and found it really amazing. The matter has been presented in a very friendly tone and easy to understand style. It really helped me to thoroughly understand the concepts. But, I would like to bring into your consideration a small mistake from the book. In the chapter 'Using Transistors to Build Primitive Logic Functions' it is written that for building a CMOS Buffer, four transistors are required. But i think, interchanging the positions of the NMOS and PMOS transistors in the NOT circuit (given in the book) can give a Buffer and this technique uses only two transistors. Please find an image file attached with this email with a circuit diagram.   Am I right? Or is there a flaw in the above technique? Except for this, I found the book very good and I will surely recommend it to my peers. Thank you sir for your consideration. Well, you have to admit that he writes a very nice message. So there I am sitting looking at his suggested circuit. I can absolutely see where he's coming from. At the same time, I know this won't work, because I know you can't connect the PMOS and NMOS transistors together in this way. The problem is that – as I mentioned above – my poor old brain is limping along at a fraction of its usual speed, and I find myself unable to articulate why this won't work. What say you? How can we put this into words that he (and I) will understand?  

The How Things Work group on Yahoo is moving from one topic to another with the agility of a mountain goat. Someone just gave a link to an article along with this message saying "This is an amazing piece of work that seems to have no history." Since I love robots and the subject of the message was "Interesting robot dog from the 1950s" I just had to bounce over there and take a look ( Click here to see the article). It seems that Daniel C. Dennett – a professor at Tufts University in Massachusetts – spotted this unusual robot dog in a shop in France and he quickly snapped it up. (I don't blame him – if I'd seen something like this I would have bought it without thinking.) This is just so amazingly cool. It's almost a retro version of Doctor Who's robot dog K-9 (I remember thinking K-9 was so cool when I was a kid ... but truth to tell I'm glad he's no longer with the Doctor apart from the occasional guest appearance). But let's not wander off into the weeds... take a look at the picture below and see what you think:   So now the big question is "Who made this little beauty and why?" I would also like to know just what it's capable of, because it looks much too sophisticated for a radio controlled model. It appears to pre-date integrated circuits, so I'm assuming that it's transistor-based and uses analog environmental detection (proximity, touch, light, sound?) and control functions. Ooooh! I would love to get my hands on this...

The How Things Work group on Yahoo is jumping from topic to topic with the agility of a mountain goat. Someone just provided a link to an article along with a brief message saying "This is an amazing piece of work that seems to have no history." Since I love robots and the subject of the message was "Interesting robot dog from the 1950s" I just had to bounce over there and take a look ( Click here to see the article). It seems that Daniel C. Dennett – a professor at Tufts University in Massachusetts – spotted this unusual robot dog in a shop in France and he quickly snapped it up. (I don't blame him – if I'd seen something like this I would have bought it without thinking.) This is just so amazingly cool. It's almost a retro version of Doctor Who's robot dog K-9 (I remember thinking K-9 was so cool when I was a kid ... but truth to tell I'm glad he's no longer with the Doctor apart from the occasional guest appearance). But let's not wander off into the weeds... take a look at the picture below and see what you think:   So now the big question is "Who made this little beauty and why?" I would also like to know just what it's capable of, because it looks much too sophisticated for a radio controlled model. It appears to pre-date integrated circuits, so I'm assuming that it's transistor-based and uses analog environmental detection (proximity, touch, light, sound?) and control functions. Ooooh! I would love to get my hands on this...