> However, I would like to amplify the output of the 5 bit DAC
> of a PIC microcontroller (PIC18F46k22) to drive a small speaker.

Speaker needs to be in collector circuit to amplify voltage.
When in emitter you get current gain =3D buffer.
That MAY be what you wanted deep-ending on DAC output.

In your circuit it's not getting to the linear[tm] region that is sought so
much as to get enough current to allow enough power to get enough audio.
Base bias must set DC point for speaker which is ~~ 0.6V lower than Vbase.
A 10k pot Vcc-gnd with base on wiper will teach you much. Put say 1K on Vcc
end of pot in series to stop magic smoke escaping from transistor.


______________

Crude common collector. May even work.

C1 100 uF
C2 100 uF

R1 Hasta la Resista? </Whoops>
R2 27 Ohms
R3 39K
R4 12K

DAC C1A
C1B Q1B

Q1E R2A
R2B GND

Q1E C2A
C2A GND

VCC SPKRA
SKRB Q1C

VCC R3A
R3B Q1B

Q1B R4A
R4B GND


Smaller R2 =3D Re =3D more current.
Smaller R3 =3D larger base voltage =3D more current.

Will need to play for Max Headroom [tm]

~~~ 20 mA as specified above.

E&OE.

          R
--=20
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