This amplifier for hearing aid was found in a 1968 documentation using an integrated of the time. The power is from a battery, the consumption of 1.65 mA and the power of about to 1 mW.
Using a voltage comparator, we find this AND gate on a Popular Electronics from the 90s. The...
This crystal oscillator circuit is indicated for use as a frequency reference in the calibration...
Any operational amplifier can be used in this circuit. The 741 is the most common. Power supply must...