Reverse Bias Oscillator
source: (C) G. Forrest Cook
There are a
number of npn transistors that will oscillate in the audio range when reverse biased.
Minimum supply voltage is 7V for low power transistors such as BC109, BC238 and 2N2222A,
it becomes 12V for medium power transistors such as BD139 and is 16V for power transistors
as BUX22 and 2N6543. Current drain is 4mA at 9V and frequency of oscillation is 550Hz. The
base is normally left open.