Sorry for asking a non-keil related question. I have a microcontroller that generates some noise by a PWM signal / speaker. I use three NPN transistors as audio boosters. My power source is momentarily a power supply of 9V 750mA (will be batteries on the end). Can you recommend a way to boost the volume and to generate very high frequency sounds? Is there an advantage to use an audio amplifier rather than NPN transistors if I don't care about sound quality?
How are you using PWM? If you just want a noise, wouldn't just a square wave be adequate?
How are you using the 3 NPN transistors? What kind of audio output transducer are you using?
For maximum amplitude, use "bipolar" drive - like a bridged audio amp.
Thanks for your reply. I am indeed using a square wave. The three NPNs are connected emitter to base - that arrangement seems to work fine. I am using a simple 8 ohm speaker. Can you recommend a specific bridge IC?
Consider using an audio transformer, it's what they are designed for. They simplify matching the speaker impedance, block any DC, isolate the circuit 0v from the speaker -ve.