Inverter Amplifier (CB6431E)

This high input impedance circuit was found in a Popular Electronics of the 90s. The circuit supports modern operational.

Stereo Headphones Amplifier (CB982E)
The circuit presented in the figure is an amplifier for stereo sources with the Maxim MAX9723...
Digital Pulse Rate Counter (CB16772E)
In fact, this 1994 circuit uses a scale of LEDs to indicate the pulse rate applied to its input....
Operational Bistable 2 (CB15614E)
What differentiates this circuit from the previous one (CB15613E) is the non-need to use a...