Colpitts Oscillator
Transistor 2N3904 CBE (C to g31 / B to
g32 / E to g33)
C1 = 1uF
(Negative stripe goes to negative voltage – other leg goes to j31)
C2 = 33nF
(g27-g29)
C3 = 10nF
(h29 – h31)
C4 = 47nF
(d29 – d31)
C5 = 100nF
(h37 – h39)
R1 = 15k
(h32 – positive voltage)
R2 = 5.6k
(i32 – negative voltage)
R3 = 68 (g36
– negative voltage on other side)
Jumper wires:
e29 – f29
j27 –
positive voltage
Negative
voltage – other negative voltage
j31 – j37
h33 – h36
c31 – f33
Oscilloscope probe = g39 and ground
clip attached to inductor L1’s i27 leg
Shorter
jumpers are better because breadboards have parasitic inductance that adds to
the inductor’s parameters. I had a few really long jumper wires-when I
shortened them the circuit worked.
I think C1
(the electrolytic capacitor) shorts the “Base” (B) of the transistor so that
you get an output AC wave. Oscillation = waves = alternating = AC. I forgot to
put my oscilloscope on ‘AC’ setting so I was getting weird displays.
This circuit
was much harder to get going than anything I’ve put together. Even when my Chua
chaotic circuits are misbehaving I still see something sort of cool. This thing is all or nothing.
I have some
variable capacitors I’m going to plunk in and play with to see what slight
adjustments do to the waveform and frequency.
