This crystal or galena radio was found in documentation from the 1990s. The earpiece must be a high impedance crystal or magnetic earpiece and D1 can be any germanium diode.
This circuit was found in a 90s Popular Electronics. With it, using a 4066, it is possible to...
This circuit was found in a Popular Electronics from the 90s. The circuit has temperature...
In the figure we have the basic application of an LM3900 transconductance amplifier, as suggested by...