Hello guys!
I'm quite ashamed to start my first post here with a question, but this project is grinding my wheels for quite a few days now, and i have reached a dead stop.
So, the problem is with this astable (which you can find all over the internet explained in millions of ways, but nowhere do they say about the huge negative VBE voltage which will break the transistor in the long run). Anyway, making some final checks to this project today i noticed this huge negative VBE, researched on the internet and found how to protect the transistors with the commutation diodes. Placed the diodes, made some adjustments to the capacitors, and everything is working, apart from one thing:
When the transistors switch on, there is a huge spike in the VBE (at about 1V, i'll upload a picture with the simulation). This produces a collector current of about 300mA and this is a problem, as the transistors's maximum Ic is 100mA. Even worse, the power dissipation on that spike is something like 2W, way above the 250mW maximum rating for the transistor.
So, the questions are:
1)Is it ok to leave the circuit like this, with the huge spike? (asking this as is a very short pulse which i think will not really affect the transistor in the long run)
2)If it's not ok, what could i do to solve this?
Thank you all in advance, i already spent too much time on something so simple...
I'm quite ashamed to start my first post here with a question, but this project is grinding my wheels for quite a few days now, and i have reached a dead stop.
So, the problem is with this astable (which you can find all over the internet explained in millions of ways, but nowhere do they say about the huge negative VBE voltage which will break the transistor in the long run). Anyway, making some final checks to this project today i noticed this huge negative VBE, researched on the internet and found how to protect the transistors with the commutation diodes. Placed the diodes, made some adjustments to the capacitors, and everything is working, apart from one thing:
When the transistors switch on, there is a huge spike in the VBE (at about 1V, i'll upload a picture with the simulation). This produces a collector current of about 300mA and this is a problem, as the transistors's maximum Ic is 100mA. Even worse, the power dissipation on that spike is something like 2W, way above the 250mW maximum rating for the transistor.
So, the questions are:
1)Is it ok to leave the circuit like this, with the huge spike? (asking this as is a very short pulse which i think will not really affect the transistor in the long run)
2)If it's not ok, what could i do to solve this?
Thank you all in advance, i already spent too much time on something so simple...