Circuits & Schematics

I designed and built this thing many years ago. I published the hobby circuit in the now defunct “Radio Elecronics” magazine back in 1992. The electronic circuit injects a precise 1 Amp of current into any unknown resistor, up to about ...

An inverter provides power backup for mains-based appliances in the event of a power failure. Most of the inverters available in the market have complicated circuit designs and are not very economical. Some of them produce a square-wave output, ...

Recently (5/21/25), I published a Design Idea (DI) describing a bidirectional current mirror using just two transistors and a diode, “A two-way mirror current mirror that is” ( Ref. 1 ). That circuit works well in some applications, ...

In the first part ( Ref. 1 ) of this Design Idea (DI), we saw how to use the TDA7052A (or similar) power amp to build a minimalist siren-type power oscillator, and also, having looked at that device’s distortion characteristics under various ...

When audio power amplifiers oscillate, the result is often smoke, perhaps with a well-cooked PCB and a side order of fried tweeter. This two-part Design Idea (DI) shows some interesting ways of (mis-)using a common power amp to produce deliberate ...

The voltage booster is a 'true' charge pump. When the output of the 555 is low, C4 charges from the supply via D1. When the output goes high, the positive end of C4 is forced high (to +24 V in a perfect world), and the charge is transferred ...

Introduction These ultra-simple projects are intended to provide two simple functions without the need for transformers or 'esoteric' parts. The first is a simple charge-pump voltage booster, that will raise your supply voltage by a factor ...

Designing an analog circuit can be a frustrating experience, as noted by Nick Cornford in his Design Idea (DI), “DIY RTD for a DMM” ( Ref. 1 ). With a fortnight’s struggle, I completed the design of 4 mA to 20 mA, two-wire ...

At its invention roughly four decades ago, STM (scanning tunneling microscopy) created a sensation because it was the first technology to make atomic-scale-resolution imaging a routine procedure. An essential requirement for the practical ...

The circuit in Figure 1 adds a soft muting switch with power-up/power-down muting to a line-level audio circuit. R 4 , C 1 , and JFET Q 1 quietly ground a signal in 100 to 200 msec when you close S 1 or release it when you open S 1 . Potentiometer ...