Hello,
I'm fairly new to electronics and can't really understand complex circuits yet. I do know the basics of the components, Ohm's low, voltage drops, etc. This is just a side hobby for me. So I've come across the astable multivibrator and I can't for the life of me understand a few things about its operation. Here's the circuit as an example:
I understand that the C1 and C2 take turns in turning on the cross connected transistors. Ie, C1 will turn on Q2 (eventually causing a turn-off of Q1) and C2 will turn on Q1 (causing a turn-off Q2). My main difficulty is in understanding the charging process of these capacitors. The way they are connected in this circuit doesn't look like anything I've seen before. Usually, I've seen the plus of the battery connected to the plus of the capacitor and the negative of the battery connected to the negative of the capacitor. The capacitor can be connected in series with a load or in parallel with a load. Regardless, its positive terminal should lead to the plus of the battery and the negative to the negative.
Here we have something unusual looking. First of all, the circuits use specifically polarized capacitors. So, looking at C2 for example, how come its negative side is connected to the positive terminal of the battery via R3? Its official right side is also connected to the positive (I guess?) when Q2 is turned off or negative when Q2 is turned on. That's so weird and so never mentioned in any descriptions of this circuit I've read. Yet you also read to always observe the polarity of the polarized capacitor. So yeah, for a newb like me, it's tough.
Next thing that is odd to me is that when we just turned on the circuit, I'm told that the voltage on both C1's and C2's negative side begins to positively charge through R2 and R3 respectively until one of them reaches the BE threshold voltage of 0.7V thus causing the ensuing events (let's forget about those for now). Ok, so as I mentioned before, it's hard to imagine the negative side of the capacitor being charged. But somehow it does work?
On top of it, the positive side of those capacitors (before any of them reach 0.7V on the negative side) reaches about the positive voltage of the battery (roughly). But how is that possible if the LEDs are not letting any current through yet and the positive sides of the capacitors are connected below the LEDs?
There's also the issue of negative voltage on the capacitors, but I'm not even going there yet.
I must be missing a lot of background on all this, but if anybody patient enough could enlighten me on the operation of this puzzling circuit, it would be so helpful.
Thanks!!
I'm fairly new to electronics and can't really understand complex circuits yet. I do know the basics of the components, Ohm's low, voltage drops, etc. This is just a side hobby for me. So I've come across the astable multivibrator and I can't for the life of me understand a few things about its operation. Here's the circuit as an example:
I understand that the C1 and C2 take turns in turning on the cross connected transistors. Ie, C1 will turn on Q2 (eventually causing a turn-off of Q1) and C2 will turn on Q1 (causing a turn-off Q2). My main difficulty is in understanding the charging process of these capacitors. The way they are connected in this circuit doesn't look like anything I've seen before. Usually, I've seen the plus of the battery connected to the plus of the capacitor and the negative of the battery connected to the negative of the capacitor. The capacitor can be connected in series with a load or in parallel with a load. Regardless, its positive terminal should lead to the plus of the battery and the negative to the negative.
Here we have something unusual looking. First of all, the circuits use specifically polarized capacitors. So, looking at C2 for example, how come its negative side is connected to the positive terminal of the battery via R3? Its official right side is also connected to the positive (I guess?) when Q2 is turned off or negative when Q2 is turned on. That's so weird and so never mentioned in any descriptions of this circuit I've read. Yet you also read to always observe the polarity of the polarized capacitor. So yeah, for a newb like me, it's tough.
Next thing that is odd to me is that when we just turned on the circuit, I'm told that the voltage on both C1's and C2's negative side begins to positively charge through R2 and R3 respectively until one of them reaches the BE threshold voltage of 0.7V thus causing the ensuing events (let's forget about those for now). Ok, so as I mentioned before, it's hard to imagine the negative side of the capacitor being charged. But somehow it does work?
On top of it, the positive side of those capacitors (before any of them reach 0.7V on the negative side) reaches about the positive voltage of the battery (roughly). But how is that possible if the LEDs are not letting any current through yet and the positive sides of the capacitors are connected below the LEDs?
There's also the issue of negative voltage on the capacitors, but I'm not even going there yet.
I must be missing a lot of background on all this, but if anybody patient enough could enlighten me on the operation of this puzzling circuit, it would be so helpful.
Thanks!!