This acoustic sensor was originally developed for an industrial application (monitoring a siren), but will also find many domestic applications. Note that the sensor is designed with safety... Read more
Superheterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second world war other, simpler receiver te... Read more
This broadband AM receiver enables you to ‘monitor’ the shortwave radio band. The circuit has been deliberately designed to have low selectivity and is most sensitive in the range from 6 to... Read more
In contrast to an ordinary voltmeter, the input of an oscilloscope generally has one side (GND) connected to ground via the mains lead. In certain situations this can be very problematic. Wh... Read more
Here is a high performance RF amplifier for the entire VHF broadcast and PMR band (100-175 MHz) which can be successfully built without any special test equipment. The grounded-gate configur... Read more
This circuit consists of six square wave oscillators. Square waves are made up of a large number of harmonics. If six square waves with different frequencies are added together, the result w... Read more
The gain of an operational amplifier is usually set using two external resistors. If you wish to have adjustable gain, you can use a digitally controlled multiplexer to select several differ... Read more
Electronics textbooks will tell you that a non-inverting opamp normally cannot be regulated down to 0 dB gain. If zero output is needed then it is usual to employ an inverting amplifier and... Read more
Valves are enjoying increasing popularity in audio systems. With the European ‘E’ series of valves, such as the ECC83 (12AX7) and EL84 (6BQ5), the filament voltage is 6.3 V. Depending on how... Read more
The well-known LM386 is an excellent choice for many designs requiring a small audio power amplifier (1-watt) in a single chip. However, the LM386 requires quite a few external parts includi... Read more
