it seems that i would need to parallel another pair of the bd140/139 transistors to drive 4 ohm load and i know that this circuit is completely pointless.
Seems like a reasonable start, IMHO.
I suggest adding a resistor between the emitter terminals of Q6 and Q11 to provide a means to extract stored charge from the output transistors. Another suggestion is to incorporate bootstrap drive to R29 and R30.
Good luck!
I suggest adding a resistor between the emitter terminals of Q6 and Q11 to provide a means to extract stored charge from the output transistors. Another suggestion is to incorporate bootstrap drive to R29 and R30.
Good luck!
I would not say pointless. To make a test with very fast output transistors to learn about self oscillations and compensation for that is a good idea for my eyes.
It will also be layout sensitive so there is also some things to try out.
That the product might be out of the common range and probably never used with speakers does not mean the projekt is worthless.
It will also be layout sensitive so there is also some things to try out.
That the product might be out of the common range and probably never used with speakers does not mean the projekt is worthless.
Aha.. the objectives have changed from "completely pointless" to "interesting schematics", I like that! :)
You could try trace the current through the output transistors say at 20 kHz with a current probe, do you see any anomalies?
You could try trace the current through the output transistors say at 20 kHz with a current probe, do you see any anomalies?
That’s current thru one side. Should be a half sine, which it is
Hi,
You might need more parallel BD's in order to keep them within the SOA even at 8ohms.
Even maximum Ic current is 1.5A is limited. This max is achived with only 12Vpeak at the output sinewave (12/8=1.5).
In addition, you need to derate this curve to the temprerature you plan to have on BD's case.
This curve is valid for 25C, which is just the standard specs but not real application, thus the derate need.
@No ideas um.. no, that's not exactly what was sought, I realize now I wasn't clear enough so my apology, what was sought after is the cross-conduction current going through between upper and lower output transistor, usually occurring around the 0 Volt crossing for resistive load.
Is the amplifier biased in class AB?
The bulk of the current waveform seen in post #7 is mostly caused by the 8 Ohm output load, so the cross-conduction current which is relatively much smaller can not easily be observed, the output current to the load have to be subtracted, maybe our amplifier simulator expert @lineup can perhaps help? :)
Is the amplifier biased in class AB?
The bulk of the current waveform seen in post #7 is mostly caused by the 8 Ohm output load, so the cross-conduction current which is relatively much smaller can not easily be observed, the output current to the load have to be subtracted, maybe our amplifier simulator expert @lineup can perhaps help? :)
Simulate with a square wave and light or no load. Emitter currents will have a small spike. Hang 100 ohm Rbe’s off the outputs and the cross conduction will go down to something tolerable. Even as it is, it is doubtful that it would cause trouble with a normal audio signal. If it starts oscillating for whatever reason, it would heat up.
Having seen incredibly complicated headphone amps.
This would be a simply amp with good possibility of rather low distortion.
Having a pair or so of outputs as shown would offer rather good driver to many or any headphone types.
So easy compared to the levels of insanity I have seen for headphone amps
For the comical aspect of it, being distortion would be rather good.
Have often thought for fun to do the same thing, using way way to many TO-126 devices to drive a 16 or 32 ohm speakers.
These circuits can be rather stable, But I will assume a little compensation is needed to bring the phase margin to a comfortably level.
Fun stuff.
A opamp with enough bandwidth and the speed of the devices, could achieve some rather good high frequency distortion ratings.
Slew rate of insanity also possible too.
This would be a simply amp with good possibility of rather low distortion.
Having a pair or so of outputs as shown would offer rather good driver to many or any headphone types.
So easy compared to the levels of insanity I have seen for headphone amps
For the comical aspect of it, being distortion would be rather good.
Have often thought for fun to do the same thing, using way way to many TO-126 devices to drive a 16 or 32 ohm speakers.
These circuits can be rather stable, But I will assume a little compensation is needed to bring the phase margin to a comfortably level.
Fun stuff.
A opamp with enough bandwidth and the speed of the devices, could achieve some rather good high frequency distortion ratings.
Slew rate of insanity also possible too.