You could tighten-up your layout quite a lot. You don't want to have large diameter current loops if you want clean fast waveforms. You also want to minimize wiring inductances where possible.
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Some more waveforms.
If you add a 1uH inductor in series with the power source in the idealized simulation schematic, almost gives same ringing waveforms... that is why I am asking the above questions.
-Using T5 to provide the 10.5 V faster in order to not wait for the storage time of T1 is a master trick, but I think there is shoot-through for a little amount of time from VS1 through T5 through T1 and ground, isn't it ?
Here are some more close-up shots showing the tight layout on the pcb.
and secondly I thought that since it's sub-MHz it would be sufficient
The frequency does not have anything to do in this specific application. It is the ON time pulse width and rise and fall times of the control source what is important here.That's tight, isn't that more like GHz tight?
The frequency does not have anything to do in this specific application. It is the ON time pulse width and rise and fall times of the control source what is important here.
Even with a 1 Hz frequency square wave signal with 50 ns ON time, your first layout would not work because of high stray inductances. The ON time is so short, that those high stray inductances would not allow the signal to propagate.
Furthermore, I ended up leaving out R6 (330 ohm) on the base of 2N3904 as it caused unwanted ringing on the output waveform.
I see that you have the 330 ohm on the base to GND. I mentioned in one of the earlier threads that I left that out as it caused unwanted ringing on the output pulse. Try to see if it improves your pulse shape.
I removed R7 (3.3KΩ) completely and changed C2 to 330pF
I feel you need faster transistors for Q2 and Q4 after looking at simulation plots.
The 2N3904 has a minimum fT of 300 MHz, while the BC337 lists a typical spec of 210 MHz. This seems to be evident in the simulation results. These larger transistors look more sluggish to turn on and off, with more overlap current. They appear to be adequate for the last driver stage.
Using a BC558/548 combination may be a better choice.
Be careful about increasing this value as it will demand more peak current from your input pulse source.
Below show plots with using BC548/558.
We can see that the speed-up capacitors is essential to get fast switching, but it puts a load on the input signal which distorts the shape. For this reason, you don't want to increase these values if you can avoid it.
Expanded overlay of VF1 and Gate pulses, show very good tr(18 ns) and tf(22 ns) times, which is close to the simulation results.
About your input pulse:
Is plot you are showing of this pulse due to the performance of the scope? It appears that the pulse has almost no plateau time and does not look like your initial specification.
Here are some results switching the load with a **broken link removed** device. The on-resistance is a bit high for this application, but this was at hand. The load is just four 1/4W 12 Ω axial resistors in parallel, so there is some inductive component that we can see the ringing effects of on the Vload trace. Furthermore, the probe GND leads will have some effect as well.
In the last plot, I inserted a 10 Ω series gate resistor. It slows down the switching but reduces the inductance effects to get a cleaner trace.
Yes and No, I'm confident there is a square-ish looking pulse in there, but I wanted to emphasize the pulse timing/delay which looks really good to me.
And their large leads. Also leads from the other components as well.It's a huge ring though, I would guess it could be attributed to the bulbs since the filament is coiled inside?
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