I really find your solid state videos interesting because I am somewhat knowledgeable about vacuum tubes, but not so much about solid state. Very educational to me.
In late 80s, I got a bunch of BF173 metal can, HF transistors. While I just made my high voltage regulated power supply (60-300V) with a PL509 vacuum tube, I started to wonder the same thing: what happens when a higher voltage is applied to a transistor? So, I played with this setup. I manually traced the curves you find at 10:15. I beleve that the process what happens you described well. However, I used a resistor between base and ground. With this setup,I built myself a pulse generator with 1000V pulse amplitude and 0.1us pulse width, some 50KHz frequency. It was useful to make Kirlian photos. However, it was easily influenced by the temperature. Note that tthe characteristic curve you find at 10:15 show a negative resistance after the breakdown, you can use that to make an very simple oscillator, pulse, ramp or square wave. That curve I remember to be somewhat similar to a neon lamp curve. I repeated the experiment with some more transistors and I find that for this usage, are better high frequency and high gain transistors (high ft and hfe).
Thank you for this video. It brought me back to my younger years ( I am 78 now) building audio amplifiers starting with vacuum tubes then to germanium transistors, then ventured to the then just newer silicon transistors. By the time MOSFETs came into the picture, i already shifted to other interests. This is not to say i have lost interest in audio electronics. One other reason i am posting this message is to confirm from you what I heard at 9:34 or so about the " between 5 volt to 8 volt"voltage range between the emitter- base junction to cause conduction to begin between them. Please correct me if I am wrong because my understanding is that the range of base-emitter voltage for conduction to happen between them is .5 volt to .8 volts. Silicon transistiors would need somewhere near .7 v. While germsnium transistors generally need less than .5v between base and emitter. Please continue making videos. A new subscriber here.
This is avalanche regim of the transistors, so is very dependant the temperature, junction diffusion width (i.e. transistor type, batch, technology of fabrication, etc). When I played with this, I find to be a very experimental process, as not any two transistors have for sure the same breakdown voltage. At least that is what I find many years ago and what my university teacher explained to me when I asked about the experiment.
@@JohnAudioTech yes and as you found out the breakdown is lower voltage at higher temperature. Which if that's the case makes the rating a bit suss. We'd be more interested in worst case. Which would be at max operating temp. But then I was thinking maybe that explains the difference between the rating and what you were finding? Perhaps their rating is worst case?
It was interesting to know a small reverse BE voltage kills fat transistors easily. I have a broken linear PS which kills its power tr when i short circuit it. I'm going to put a hevey diode across CE like MOSFETs. See what happens.
Nursery School in Electronics. John have you think to convert the current mirror for the 2 matched input transistors to "Miler" current mirror ? (I hope to YES)
Correction: Transistors are BD139 and BD140, not BC139, BC140.
I was wondering bc139 bc140? That dosen't sound right lol
I really find your solid state videos interesting because I am somewhat knowledgeable about vacuum tubes, but not so much about solid state. Very educational to me.
Very good tutorial on break down voltage in transistors.
In late 80s, I got a bunch of BF173 metal can, HF transistors. While I just made my high voltage regulated power supply (60-300V) with a PL509 vacuum tube, I started to wonder the same thing: what happens when a higher voltage is applied to a transistor? So, I played with this setup.
I manually traced the curves you find at 10:15. I beleve that the process what happens you described well. However, I used a resistor between base and ground. With this setup,I built myself a pulse generator with 1000V pulse amplitude and 0.1us pulse width, some 50KHz frequency. It was useful to make Kirlian photos. However, it was easily influenced by the temperature. Note that tthe characteristic curve you find at 10:15 show a negative resistance after the breakdown, you can use that to make an very simple oscillator, pulse, ramp or square wave. That curve I remember to be somewhat similar to a neon lamp curve.
I repeated the experiment with some more transistors and I find that for this usage, are better high frequency and high gain transistors (high ft and hfe).
Thank you for this video. It brought me back to my younger years ( I am 78 now) building audio amplifiers starting with vacuum tubes then to germanium transistors, then ventured to the then just newer silicon transistors. By the time MOSFETs came into the picture, i already shifted to other interests. This is not to say i have lost interest in audio electronics.
One other reason i am posting this message is to confirm from you what I heard at 9:34 or so about the " between 5 volt to 8 volt"voltage range between the emitter- base junction to cause conduction to begin between them. Please correct me if I am wrong because my understanding is that the range of base-emitter voltage for conduction to happen between them is .5 volt to .8 volts. Silicon transistiors would need somewhere near .7 v. While germsnium transistors generally need less than .5v between base and emitter.
Please continue making videos. A new subscriber here.
Videos that I watch without getting bored...
tutorial and visual..
We even heard the sounds of the amplifiers you made, thank you.
Always have time for you John.
I like to see videos like this. Thanks
Very glad thank you!
Thank you
Very nice. Thank you sir.
good video
Helpful
Would you care to post a link to the diagram shown at 10:15 in the video?
Thanks
That heat leads me to believe there's more here than we've seen. Or is the rating given at a temperature?
Data sheets usually indicate that the measurements were taken at some temperature, such as 25 Deg C.
This is avalanche regim of the transistors, so is very dependant the temperature, junction diffusion width (i.e. transistor type, batch, technology of fabrication, etc). When I played with this, I find to be a very experimental process, as not any two transistors have for sure the same breakdown voltage. At least that is what I find many years ago and what my university teacher explained to me when I asked about the experiment.
@@JohnAudioTech yes and as you found out the breakdown is lower voltage at higher temperature. Which if that's the case makes the rating a bit suss. We'd be more interested in worst case. Which would be at max operating temp. But then I was thinking maybe that explains the difference between the rating and what you were finding? Perhaps their rating is worst case?
clamp 4 to 5 silicon diodes parallel to the LED. This will clamp the voltage over the LED and saves it's life.
Hey john i made a ab amp but there's a problem i cant fix...if possible can i cantact u somehow?
It was interesting to know a small reverse BE voltage kills fat transistors easily. I have a broken linear PS which kills its power tr when i short circuit it. I'm going to put a hevey diode across CE like MOSFETs. See what happens.
Nursery School in Electronics. John have you think to convert the current mirror for the 2 matched input transistors to "Miler" current mirror ? (I hope to YES)