This LM380-based circuit was found in documentation from the 1980s. The components are current, and the transistor may be a general-purpose equivalent. Note the use of a medium impedance speaker.
Combined with the two previous circuits, we can create a simple multimeter with this circuit. The...
This 1.5V instrumentation amplifier was found in National Semiconductor documentation from the...
This simple circuit helps to save incandescent lamps by leaving their filament slightly heated and thus...