This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit uses a diac and the transistor can be general-purpose.
We can implement this filter with more modern equivalent operational amplifiers, since the LM110 is...
This stethoscope or amplifier for hearing aid using a crystal headset and microphone was found in a...
The normal use of a 4520 as a divide-by-16 counter is shown in Figure bellow. In the normal...