We found this circuit in a 1977 documentation. The National Semiconductor's LM380 is no longer easily found, but if used on this amplifier it provides excellent reproduction quality.
The circuit shown in the figure can be useful in cases where a common telephone extension is used....
This circuit uses two operational amplifiers that admit equivalents. The configuration is from...
This circuit was found in General Electric documentation from 1966. The circuit is suitable for any...