I'm learning about how to combine common-collector stages for an audio amplification project, and clearly there is something I don't understand. The circuit shown combines 5 stages of emitter followers. I've designed stage each to have a DC bias point of one diode drop above 0.5Vcc. Each stage has an output impedance far less than the subsequent stage's input impedance (about 1/20). Unfortunately, it doesn't work. The output voltage (before the output capacitor) rises to about 16.7 volts but refuses to go below 9.55 volts, making a horribly distorted output signal.
If the stages were numbered 1-5 from left to right, here are the impedances I calculated:
Stage 1: Rin = 12.5k, Rout = 125 Stage 2: Rin = 2.5k, Rout = 25 Stage 3: Rin = 500, Rout = 5 Stage 4: Rin = 100, Rout = 1 Stage 5: Rin = 20, Rout = 0.2
I used a 10v amplitude (20v p-p) input signal at 1 kHz.
I set the input capacitor to 2 Hz and the output capacitor to 20 Hz to act as a 20Hz. high-pass.
I know there are other solutions better-suited to these needs such as a Darlington, cascode, push-pull, etc. I'm not interested in other ideas, but merely seeking to understand how CC stages can be coupled together. Here's the question:
How do I design multiple CC stages to follow one another so that there is no distortion?
As for design specs, Vcc is 24v and I'm hoping to be able to drive an 8ohm speaker at something around 0.5 to 1 watt from 20Hz to 20kHz.