Operational Amplifiers in Practice

The final instalment of the short series on opamp basics explores some of the more unusual features of operational amplifiers. Another topic is opamps with power outputs.

Too many electronics enthusiasts harbour a certain reluctance to enter the world of microcontrollers and programming. It really is not so difficult, as we will show by introducing four low-cost boards. You will see the setup and how some simple demo programs can be run so that early success is guaranteed. To get things going we gave a low-cost Arduino board to Burkhard Kainka who is one of our long-time contributors to Elektor and a specialist in many fields of electronics. His son Fabian will be giving us the lowdown on the NodeMCU board — a platform designed especially for IoT applications.

In many applications it is essential to use an opamp with extremely high impedance inputs. In these cases a standard bipolar device will not do the job, and instead we must use an opamp with FET (field-effect transistor) inputs.

The SDR Shield 2.0 introduced in ElektorLabs Magazine edition 4/2018 offers a broad range of opportunities, not only for broadcast reception but also for amateur radio applications. You can hear SSB signals, also listen to CW and numerous digital signals for which you will need additional software to be able to decode them.

Every microcontroller that features an A-to-D converter and a PC interface can be used as a logging device for data acquisition systems. But with the BBC micro:bit you get the bonus of a small LED display and a wirefree interface into the bargain. Just the job for special applications in your electronics lab!

Using optics for switching and control is a widely employed and accepted technique, with many favorable features. No mechanical movement, no wear and tear on switch contacts, modules are electrically isolated and much more.

Sure, an Arduino also offers a range of inputs and outputs but the BBC Micro:bit offers additionally numerous sensors and control functions. Two input buttons and a 5x5-LED display field, a compass sensor and a 3-axis accelerometer, plus light and temperature measurement. As the crowning glory you have Bluetooth Low Energy (BLE) data transfer.

Although the theremin was invented nearly 100 years ago, the instrument still has enthusiastic fans. It is played entirely without physical contact, and almost everyone will have heard one at some point. The original design from 1920, by Lev Termen, alias Léon Theremin, used vacuum tubes, but JFETs can equally well be employed. In this article we look at the development of an experimental design for a theremin that you can build yourself.

Ever since the earliest days of telegraphy, electrical communication has been possible over a single wire. Today the 1-Wire Bus and similar protocols function using just one conductor, without the need for an additional clock line. Infrared (IR) remote controls operate on similar principles. In this session we get to grips with temperature and humidity sensors among other things, and in particular with the IR Transmitter and Receiver in Elektor’s 35 Sensors Kit.

Can we also use the SDR Shield with just an Arduino and no PC at all? Certainly we can. It’s entirely feasible (with a few restrictions) because all of the vital control functions are available on the Elektor Extension Shield. The only task that remains then is processing the IQ signals.