Avalanche Breakdown Photoemission and the Photoelectric Effect in Bipolar Transistors
Or
World's Simplest Positive to Negative Power Supply Converter.
By utilizing avalanche breakdown photoemission and the photoelectric effect a transistor can be made to supply a negative current source from a positive power supply. Current "gain" was measured.
Or
World's Simplest Positive to Negative Power Supply Converter.
By utilizing avalanche breakdown photoemission and the photoelectric effect a transistor can be made to supply a negative current source from a positive power supply. Current "gain" was measured.
Figure 1. The test fixture used to measure
the avalanche current and photoelectric current.
Check for updates at www.projects.cappels.org
The Concept
Figure 2. Circuit that demonstrates the effect. Avalanche current for the emitter is taken from a positive power supply. Notice the polarity of the current meter.
Light is generated in the base-emitter junction of
bipolar transistors when the reverse biased junction is avalanched.
Some of this light causes the photoelectric effect in the base-collector
junction, which can be observed as either a voltage across the
base-collector junction or a current through the junction. The
photoelectric current in the base flows in the opposite direction of the
avalanche current through the base, thus enabling the generation of
negative voltage or a negative current from the collector with respect to the base with a positive power supply.
The maximum observed open circuit output voltage was a little more than 0.3 volts.
The maximum observed open circuit output voltage was a little more than 0.3 volts.
The measurement fixture
Figure 3. Measurement fixture.
Photo currents were measured in the fixture shown in Figure 3. The reverse breakdown characteristics varied according to individual transistors, so the input voltage was adjusted to obtain approximately 20 milliamps for each transistor.
TABLE 1. NPN TRANSISTORS, SMALL SIGNAL
