We found this micro amplifier in a technical documentation from National Semiconductor. The circuit can be used on an experimental phone, being powered even by alternative power sources.
The circuit of the figure can provide voltages of 5, 8.9 and 12.5 V at its output, all doing this...
In the figure we have an application of ON Semiconductor's own semiconductor manual from the 80's....
This circuit was found in Philips documentation from 1969. The components are from the time...