DickCappels
- Joined Aug 21, 2008
- 10,170
About US$0.01 per watt in single-ended configuration, about the price of one TIP41.
Correction. . . a tenth, not a third. It would require a third of the voltage.You speaker is very inefficient at 86dB. You can get similar speakers that are 96dB. They would require 1/3 the power to produce the same sound level, and therefore would run 3 times as long on the same battery.
Input impedance is set by R15 = 22k386 ohm resistance is too low for my circuit? Well at least thats the sum of resistances entering the transistor bases unless I'm missing something
It's down to the difference between the Vbe voltages and the diode forward voltages. If the diode voltages are too high, then the transistors have more Vbe which leads to more collector current and therefore more heating.I'm trying to figure out how the 56 ohm resistors would melt the transistors. TIP41 datasheet states maximum continuous base current is 2A. If I were to pretend the 330 ohm resistor is a short, then doing math, I get 14.4/56=257mA, I guess its because doing further math leads to 3.7W. I think they would want to fry in this case only if good heatsinks aren't attached.
NO - its the bias - @DickCappels mentioned it as long ago as post #19Maybe its my speaker that is causing the TIP41 transistors to be hottish.
I modified my circuit a bit so the pull-up resistors audioguru referred to have been doubled in value and I now used a 6V supply and when I did tests, the audio is clear but the TIP41 transistor was getting warm.
Im betting everything comes down to the speaker because its only 8 ohms and doing math on voltages 6 and up gives me wattages greater than 2. Maybe my bet is wrong...
You will almost certainly achieve lower output without the bootstrap capacitors. By removing them, you prevent the drive voltage to the positive output transistor going above the supply voltage. If you see the opposite, it must be due to an effect somewhere else in the circuit.I noticed something else. I was playing with more values in spice and when I made the bootstrap capacitors almost non-existant (setting them from 1000uF to 1pF each) I was able to achieve higher amplitude.
A real speaker is approximately 6Ω in series with 600uH (neglecting the bass resonance, which rarely makes any difference to the performance of an amplifier)Its probably because I'm using the 8 ohm resistor tied to the outputs to simulate a speaker and probably that 8 ohm resistor is almost pulling the outputs together. Is it a bad idea to simulate this 8 ohm resistor as a speaker in spice? I couldn't find a speaker symbol in spice.
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