Using 4 operational amplifiers this circuit generates 4 different tones. The circuit is from an American documentation from the 90's. Operational amplifiers are tTL084.
This amplifier circuit for instrumentation was found in the manual of the used integrated circuit...
We can use this amplifier with low impedance headphones with good performance. Possible...
This circuit was obtained from the November 1989 issue of Radio Electronics magazine. The circuit is...