1 2 3 4 Previous

55 posts

# Op Amps: NIC (Negative Impedance Converter) and the Chua Oscillator

Posted by jc2048 May 4, 2019
Introduction   NIC stands for Negative Impedance Converter. It's one particular circuit configuration that can exhibit the phenomena of negative resistance. I'm going to look at that first and then, once we've done that, I'm going to use a pair of them to power a rather curious oscillator circuit due to Chua (the fun bit).   An Op Amp Negative Impedance Converter   As I'm sure you all know, a simple passive resistor has a property called resistance. The resistance is the con ...

# Chaos

Posted by jc2048 Apr 30, 2019
I've just been playing with Chua's circuit, using a couple of op amps for the negative resistance element. It makes for some pretty XY plots on the oscilloscope. Thought you might like to see them.       It's very finicky getting the values right and you can see from the bottom trace that it's not very stable, but it's good fun to play with.   Here's a link to the follow-up blog where I go into more details about the circuit I was using: Op Amps: NIC (Negative Impedanc ...

# Transistors: Saturation Part 2 and Inverse Mode

Posted by jc2048 Feb 12, 2019
This is another exploratory blog relating to bipolar junction transistors (BJTs). It follows on from a previous blog which can be found here Transistors: Saturation   Be aware that I'm not an expert in all this: I'm studying it and you're looking over my shoulder as I experiment and explore the subject. So this is not a tutorial and it's possible that some of my explanations may, at times, be wrong. 　  Introduction 　  In the previous blog I looked at the collector and base s ...

# A Transistor Load: How it Works

Posted by jc2048 Dec 30, 2018
A Transistor Load A Transistor Load: Stability A Transistor Load: Stability Part 2   Introduction   Important note: I'm learning about design with transistors and this is an investigation of transistor design techniques and presents a first prototype of a possible circuit, it's a long way from being a finished project suitable for replication.   I said in the original blog that I'd explain how I arrived at the design, so in this blog I'm going to give a quick run- throu ...

# A Transistor Load: Stability Part 2

Posted by jc2048 Dec 29, 2018
Introduction   This is a short follow-up to A Transistor Load which I blogged about as part of the Project14 Test and Instrumentation competition.   In the last blog A Transistor Load: Stability I got as far as compensating the amplifier section with a single 'dominant pole' capacitor and looking at the way the dynamic response was affected by different capacitor values. I also looked at the issue of lead inductance in the output current loop. I've done a little bit more work on ...

Posted by jc2048 Nov 27, 2018
Introduction   This is a follow-up to A Transistor Load which I blogged about as part of the Project14 Test and Instrumentation competition. Since then I've been looking at the way the load performs, so this blog is on the subject of stability. By 'stability', I mean not only whether there's the possibility of the circuit breaking into sustained oscillations, but whether we might be close to that and the waveforms might ring badly (damped oscillations). To do this, I'm going to use th ...

Posted by jc2048 Oct 24, 2018
Electronic Art   9 Pieces of Pi: Slice 1: The Long Way Round 9 Pieces of Pi: Slice 2: Manifesto for Art Electronic 9 Pieces of Pi: Slice 3: Trickle Down to the Brave New World (This Way!)     micro:bit   The micro:bit Quartet PWM [micro:bit] Light Seeking Light Doth Light of Light Beguile [micro:bit] IO, IO, it's off to work we go! [micro:bit].   Arduino   Cool LED Displays: Boost That LED!   A Simple Arduino Music Box Simple Arduino Music Box: Voi ...

# Mr Moog's Fabulous Filter

Posted by jc2048 Oct 2, 2018
This blog is about a ladder. Another one.   A few days after I had finished the series of blogs I did on the R-2R resistor ladder I was in my local library, browsing the shelves in the way that you do, when I came across a book [1] on the history of the early days of analogue electronic music synthesizers - it was specifically about the Moog Synthesizer Co, though with lots of references to his main competitors: Bucchla, EMS, Oberheim and so on. It was an interesting read, though it focuse ...

# Op Amps - The Norton CDA

Posted by jc2048 Aug 30, 2018
Introduction   This blog is a bit off the beaten track and features an unusual form of op amp called a Norton amplifier. Perhaps I should have called it 'Op Amp Inessentials'! If it's not your kind of thing, skip it and go on to something more interesting.   The devices have been around for a long time but I've never had any cause to use one in a design. People are obviously still using them, though, as TI (who now own National Semiconductor) still list and sell the device I'm go ...

# Op Amps: Simulating a Two-Phase Oscillator

Posted by jc2048 Aug 9, 2018
Introduction   Even more oscillators!   At some point, for reasons I can't remember now, I tried simulating some simple sine wave oscillators. At the time they all got left in the simulator's default save directory which is where I've been retrieving them from.   The last blog looked at a very simple and, to be honest, not very good single-transistor design Transistors: Phase-Shift Sine Wave Oscillator   This one, in contrast, uses op-amps to provide the gain and p ...

# Transistors: Phase-Shift Sine Wave Oscillator

Posted by jc2048 Jul 19, 2018
Introduction   More oscillators!   At some point, for reasons I can't remember now, I tried simulating some simple sinewave oscillators. Here's one of them. This one uses a single transistor to provide the gain and a series of RC elements to provide the phase shift. The original circuit might have been from one of Graf's collections of circuits (I borrowed the Oscillators one from the library last year), though it's a fairly common circuit and you'll find it reproduced elsewhere. Boo ...

# The Ramp-O-Tron

Posted by jc2048 Jul 17, 2018
INTRODUCTION   More oscillator odds and ends. These aren't complete projects, just bits of tinkering and trying things out but they may be of interest for all that.   This one started out as playing with the simulator. The circuit itself came from an old applications manual published in the 1970s by Ferranti[1] (they later became Zetex and then a part of Diodes Inc), though the original didn't have the loudspeaker - I added that.   A RAMP GENERATOR   This is a ramp ...

# 555cc

Posted by jc2048 Jul 9, 2018
This is some more experimenting and general 'fiddling around' sparked off by the Project14 Simple Music Maker challenge.   555 timers have been around for a long time. When the UK electronics store chain Maplin went out of business a couple of months ago, amongst the devices that I bought in their closing down sale were some 555s. I was curious to see if I could get a 555 timer producing a reasonable triangle waveform and that's the subject of this blog. It's not a project. It's not a ...

# Uni-Tunes

Posted by jc2048 Jun 19, 2018
Introduction   In the course of doing the Simple Music Maker I experimented with a few other odds and ends, both as real prototypes on a breadboard and messing around with the simulator. Here's one of them. I'll blog about a couple of the others, too. These aren't complete projects, just a bit of tinkering and trying things out, but they may be of interest for all that.   When I was in my teens and first developed an interest in electronics, one of the projects I built back then ...

# Simple Arduino Music Box: Chimes

Posted by jc2048 Jun 5, 2018
Like sweet bells jangled, out of tune and harsh;   Ophelia, Hamlet [III, 1], William Shakespeare   Previous blogs: A Simple Arduino Music Box Simple Arduino Music Box: Voices Simple Arduino Music Box: Chords Simple Arduino Music Box: Envelopes   Introduction   I'm discovering that, if you build a simple, programmable device to make sound, you can't stop playing with it. With each of these blogs I say to myself that it's going to be the last, and yet here I am doi ...

By date: By tag: