Pair with Piezo Sensor

One transistor can feed its amplified signal directly to another, and this is called the Darlington circuit, named after its innovator. If each transistor has a gain of about 100, the overall gain is about 10,000. They can be bought in a single 

The inexpensive piezo devices used in this course were not designed for use as microphones, and they work best if the black leads are made positive. A small loudspeaker (electromagnetic, with a paper cone) can serve as the other transducer, converting an electric signal back into mechanical sound waves. However, if it is not available, another piezo can be used in its place. 

Battery, nine volts Clip leads, 14 inch, one set. 

Lamp bulb, tungsten, 12 volt dc, green or blue Multimeter (or multitester ) 

Resistors, 330 ohms, IK, lOK (1/2 or 1/4 watt) Resistor, Power, 100 ohms (1 or 1/2 watt) Potentiometer, 5K 

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