Dec 10 2020
With the current amplifier nearing completion, I am looking into the possibility of building an amplifier with more power output. At present it is not clear to me how two transistors can improve the voltage swings as opposed to one transistor, since the voltage that is being regulated, that is between 6V and 15 V , will remain the same.
Starting with some measurements, the output of a phone headphone out is listed as 0.15 V. Testing with a multi-meter in alternating voltage mode, this showed 0.2 V maximum with music, and 0.1 V with a sine wave output from the same headphone out. So this 0.15 V is what the speaker has to take and turn into sound.
What is the output from a single transistor amplifier? What is the increase in voltage swing with two transistors connected to each other? This is what we have to find out.
I obtained some spurious readings of 0.7V when not connected to anything, however when the multi-meter was connected to my TEA 2025 amplifier speaker output terminals at one of the speakers. The output came up to a 2.4V and more. This means that the output to a speaker can be 2 Volts or more (not very loud after all).
The point pg the matter is hat the 2 Volts is well below the maximum volts swing of 5 volts that the transistor is capable of,, or at lease much less than the power supply voltage. Assuming the transistor is capable of. cutting off the power supply and allowing the maximum current to go through, I assume there is some scope for improvement.