Found in Motorola documentation from the 90's, this circuit has a high input impedance. The power supply must be symmetrical. The circuit can be implemented with modern operational amplifiers.
Figure 1 shows a circuit than can be used as time stage in timers, and other applications....
This circuit is from a 1989 Electronics Handbook. The zener diodes are 9 V x 1 W and the...
We can use this amplifier with low impedance headphones with good performance. Possible...