Astable Multivibrators - 1
I built an astable multivibrator from discrete components:
I used 2N2222 transistors instead of BCS547.
Here’s what that schematic looks like on a breadboard:
This is the circuit’s outputs, powered at 5.0V, 2.16kHz
Just like the schematic says, one output is the mirror-image of the other.
Frequency - calculated vs measured
I tried to figure out how fast the circuit should oscillate.
Here’s the most sensible reference I could find.
According to that web page’s formula, values of 47K Ohm and 10 nF should give a 1541 Hz frequency output.
RC circuits aren’t supposed to be affected by the input voltages, but the frequency of my breadboarded circuit, as measured by oscilloscope, varied a lot with voltage.
|< 1.3||<10 to 85 Hz, unstable|
The capacitors measured 6 nF and 7.5 nF, which the resistors measured 46.5K Ohms. The difference in capacitance shows up in the slightly different pulse length in the oscilloscope trace above.
The as-measured frequency is:
f = 1/(0.69*6e-9*46500 + 0.69*7.5e-9*46500) = 2.3 kHz
That’s a better match to the measured frequency, but why the frequency variation with voltage?