We found this circuit in the Linear Applications Handbook by National Semiconductor. It uses the LM3900, an operational transconductance amplifier as a base. Q1 can be a 2N2222 or similar.
The filter shown in the figure, suggested by Motorola, operates at a cut-off frequency of 1 kHz,...
The purpose of this circuit based on Maxim's MAX9022 is to find faults in multiple cables. The...
This circuit is suggested by Motorola in its 1990 Linear Databook. The speaker (or headphone is 32...