Hi all,
I've build the astable multivibrator with 2N2222 transistors. As you'll find many examples of on internet.
All works, but I'm still wondering why it won't start oscillating after cold start.
I've read other threads and they mention for example "Since no two devices are identical, one or the other will have slightly higher gain than the other. The one with the highest gain will start to conduct slightly more than the other. That slight difference results in the collector of that transistor starting to drop voltage slightly." as why it would start oscillating.
However mine just won't start on it's own, I have to pull one side to ground for it to start.
I've attached some images from my oscilloscope. Probes are on the + side of the capacitors.
What I noticed is that both charge up 'till 188mV initally (InitialPower.png), which is the bottom voltage when it's oscillating. Then I hit the 'reset' button (afterReset.png) causing the 2nd capacitor to go to 0V and in turn causes a little spike in the first capacitor. Then it starts oscillating (the other two graphs).
Reason for my question is that all sites describing on how to create this circuit, don't mention this behaviour. That made me question my setup.
The circuit is build according to 'circuit.png', see my circuit in circuit2.jpg. With:
C1/C2: 100μF
Q1/2: 2N2222
R1/4: 1k
R2/3: 10k
VCC: 5V
Hopefully someone is able to give me some insights in what's happening.
And if more info is needed, just let me know!
KR,
Onno.
I've build the astable multivibrator with 2N2222 transistors. As you'll find many examples of on internet.
All works, but I'm still wondering why it won't start oscillating after cold start.
I've read other threads and they mention for example "Since no two devices are identical, one or the other will have slightly higher gain than the other. The one with the highest gain will start to conduct slightly more than the other. That slight difference results in the collector of that transistor starting to drop voltage slightly." as why it would start oscillating.
However mine just won't start on it's own, I have to pull one side to ground for it to start.
I've attached some images from my oscilloscope. Probes are on the + side of the capacitors.
What I noticed is that both charge up 'till 188mV initally (InitialPower.png), which is the bottom voltage when it's oscillating. Then I hit the 'reset' button (afterReset.png) causing the 2nd capacitor to go to 0V and in turn causes a little spike in the first capacitor. Then it starts oscillating (the other two graphs).
Reason for my question is that all sites describing on how to create this circuit, don't mention this behaviour. That made me question my setup.
The circuit is build according to 'circuit.png', see my circuit in circuit2.jpg. With:
C1/C2: 100μF
Q1/2: 2N2222
R1/4: 1k
R2/3: 10k
VCC: 5V
Hopefully someone is able to give me some insights in what's happening.
And if more info is needed, just let me know!
KR,
Onno.
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