That's not going to help much. You need a few more things. What is your simulator saying the current flow is through Q1 and Q3 (collector current?guess ill have to add 4.7 ohm emitter resistors.
My last design had heat but not as much as this design but it didn't have emitter resistors but was using 7.2V. then again the resistors in the old design were 330 ohms and 56 ohms but if I use values too high then the sound output wont be loud
The emitter resistors made the waveforms worse.That's not going to help much. You need a few more things. What is your simulator saying the current flow is through Q1 and Q3 (collector current?
The tab on those transistors is connected (electrically) to the collector pin (middle pin). You would be shorting across the load if you connect all four. You can connect the left NPN to the left PNP but, your circuit may not be optimal.You know what I think might be going on... I think there's a resistance in each TIP transistor that is going in parallel with the external resistances because the external resistances alone will give me worst case 7.2/82 = 87mA. 87mA x 7.2 = 0.632W
But based on simulator data, measurements with same values is 381mA and that x 7.2 = 2.74W which means TIP transistor needs a heatsink to be OK.
since I'm low on heatsinks and all TIP transistor holes connect to the same place electrically, would I be able to connect them all together using thick wire and solder as a giant heatsink and then connect that to the same signal on the PCB?
You‘ve not copied that correctly. The cathode of the lower diode goes to the base of Q3 - it’s a standard push-pull output stage.The PNP Tip42 will be off while the TIP41 NPNs are on. But...
The R8 and R6 are pulling Q1 base up and turning on current flow.
Once current flows through Q1, the base of Q7 is pulled high to turn it on.
theat pulls the base of Q3 low (a PNP) and it turns on.
nowmyou have Q1 and Q3 on to connect 7.5v to ground (essentially).
this is the fragment that could be improved. Caps removed to show DC steady state current flow.
View attachment 277366
Why don‘t you read my post when you asked the same question in your previous thread.View attachment 277363
Why would the TIP42 transistors become hot in a matter of seconds as soon as I start it up?
Emitter resistors we’re mentioned in the previous thread as well (@DickCappels post #19)It may help with long term thermal management if the bias diodes are in thermal contact with the output transistors.
Also try emiter resistors of 0.47ohm, not 4.7ohm as you previously stated.
Can you elaborate more?Just noticed a glaring problem with the circuit, the mid voltage point for the load is not defined, meaning a standing current can flow through the load. It's made worse by the fact that it's a bridged amp, and neither side is designed with tight DC performance.
Bootstrapping increases the positive-going output swing. Therefore the idle voltage should be 0.4V higher than half the supply voltage.As in post #17, the voltage gain transistors Q5 and Q7 will ultimately determine the no signal operating point at the emitters of the output transistors which should be 1/2 supply rail. The 2N2222 specified have a gain spread from 50 to 300, and just the 22k resistor to bias them. The operating point will be all over the place, and also the gain alters with temperature too. A simple amplifier like this will never have stable operating points to make bridging possible.
When I ran such tests with and without the speaker (600uH inductor and 6 ohm resistor in series) the voltages at each output point is exactly the same. I also use the exact same components for both amps that I bridge together.The idle (no signal) DC voltages at the outputs of each amplifier on the bridged amplifier should be almost identical then a series output capacitor is not needed.
by Jake Hertz
by Jake Hertz
by Duane Benson
by Duane Benson