I have a 5 Vpp max audio signal in my circuit which I obtain from earlier stages of processing. I would like to deliver the signal to a 20W 4 ohms speaker. But since an OPAMP circuit generates the signal, it won't be able to supply enough current. How can I use transistors to amplify the current delivered? I don't think I need a common emitter voltage amplifier since the voltage is already large. What amplifier topology should I use? What kind of transistors do I need for the purpose?
I'm trying to refrain from using specific ICs and use transistors instead, and I don't need a very complicated adjustable amplifier, my only goal is be able to listen to the contents of the signal. The 20 W speaker is necessary for my application, a weaker speaker will not do. I already have a 12 V and 30 V power supply used in the previous stages.