This circuit was found in a 1975 documentation. Current general-purpose transistors can be used, and the power is supplied with relatively high voltage. The gain is 30 dB.
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...