Applications for this circuit include hearing aid, stethoscope, etc. Transistors are general purpose and powered by a single 1.5 V battery.
The circuit is suggested by National Semiconductor in its 1994 Linear Applications Handbook. The...
This circuit was found in a Popular Electronics from the 90s. The components admit equivalents and the...
This simple digital frequency meter using CMOS circuits reaches 5 MHz frequency. Input signals are...