Ing. Carlos Feldman, Buenos Airies, Argentina
Email : email@example.com
An audio amplifier made from discrete components with 2 Watts audio
power into an 8 ohm load. Carlos has used this amplifier on his AM
radio for many years.
The transistors are all direct coupled for good low frequency response, DC input blocking is provided
by C3 and C2 is the output capacitor. The output transistors Q1 and Q2
are complimentary and in emitter follower. Q5 is the first stage
amplifier, direct coupled to Q4. Q4 and active load Q3 provide
the bias for the output pair Q1 and Q2. Overall gain is controlled by
ratio R11 / R8.
Output power is about 1.5 watt into an 8 ohm load with 1.5% THD at audio frequencies. Supply voltage is 12V DC.
The frequency response is shown below and is
flat from 100Hz to 20kHz.
LTspice shows a very nice output waveform across resitive load R12.
Output analysis can be performed in LTspice see the simulation section
for more details.