I'm having an awful time trying to understand how astable multi-vibrator works. I've asked questions on stack exchange, but the help I've gotten there has been limited and largely negative.
This is a circuit diagram of a basic astable multi-vibrator utilizing two BJTs. I'm fairly new to electronics, but have bought all the necessary equipment, and have a basic understanding due to reading of the textbooks on this site, tutorials, etc. I would appreciate it if you take it easy, and dumb down your answers to the absolute minimum, haha.
As I'm having trouble understanding the operation of this circuit, it will be difficult to tell me exactly how it works in a manner I can understand. So, the following is how I PERCIEVE operation.
(Due to minute differences in components one of the transistors will turn on first. For the purpose of this discussion lets assume Q1 turns on first.)
1) Q1 turns on through R3.
2A) Current is flowing from the positive rail, through R1, through Q1 and into ground. Therefore, the current applied to the left plate of C1 is positive. Because there is no path for current to flow through R2 to ground, C1's right plate starts to go negative. This negative voltage suppresses the current flowing through R3 and keeps Q2 off.
2B) Simultaneously to the events occurring in step 2A, R3 begins to charge C2's left plate positively because current is flowing through R3, through Q1 and into ground. This keeps Q1 on.
That's as far as I get.
I also have a question in addition to understanding the operation of this circuit. Why does C1 charge when Q1 is on? It has positive voltage at the left plate, but where is it getting the negative voltage it needs on the right plate to "hold" the positive voltage on the left plate in place?
This is a circuit diagram of a basic astable multi-vibrator utilizing two BJTs. I'm fairly new to electronics, but have bought all the necessary equipment, and have a basic understanding due to reading of the textbooks on this site, tutorials, etc. I would appreciate it if you take it easy, and dumb down your answers to the absolute minimum, haha.
As I'm having trouble understanding the operation of this circuit, it will be difficult to tell me exactly how it works in a manner I can understand. So, the following is how I PERCIEVE operation.
(Due to minute differences in components one of the transistors will turn on first. For the purpose of this discussion lets assume Q1 turns on first.)
1) Q1 turns on through R3.
2A) Current is flowing from the positive rail, through R1, through Q1 and into ground. Therefore, the current applied to the left plate of C1 is positive. Because there is no path for current to flow through R2 to ground, C1's right plate starts to go negative. This negative voltage suppresses the current flowing through R3 and keeps Q2 off.
2B) Simultaneously to the events occurring in step 2A, R3 begins to charge C2's left plate positively because current is flowing through R3, through Q1 and into ground. This keeps Q1 on.
That's as far as I get.
I also have a question in addition to understanding the operation of this circuit. Why does C1 charge when Q1 is on? It has positive voltage at the left plate, but where is it getting the negative voltage it needs on the right plate to "hold" the positive voltage on the left plate in place?