Class B Amplifier 35W

Works only with 8ohm. Using 2N3055 as the power transistors will burn them out with 4ohm (maybe not burn them out immediately but will significantly lower their lifespan) Some of the preliminary specs are: - Pout - 35W - Pin - 60W - η - 59% - Output Impedance - 8ohm with 1 transistor 4 ohm with a pair. - Ripple rejection - -50dB from the regulator and maybe another -80dB from a high quality op amp will get you a perfect ripple rejection of -130dB. - THD+N - 0.01% with a few conditions. * 1st - very good filtering for the op amp supply. * 2nd - to use a very close to ideal of an op amp as you can. The year is 2015 and some great Ultra Low Noise op amps exist. It wouldn't be much of a trouble finding one. A few tips on the construction: - Use all frequency dependable negative feedbacks to keep the amp stable and impervious to self oscillations. - Filtering for the driving stage is also strongly advised, if not necessary. - For 4 ohm loads and 75W power add another pair of transistors in parallel to distribute the current through them. Ballast resistors will become necessary. - Mount the LED's on the heatsink where the power transistor are so as to provide some thermal stabilisation feedback, besides the Voltage Negative Feedback. This will grant you complete stability of the output no matter the conditions. Many different stabilisation examples exist using thermistors, resistors, diodes, transistors which fix thermal drift issues. - Power supply is based around a 10A diode bridge IC attached to a heatsink and filtering capacitors of no less than 4700uF! Any lower may deteriorate quality or low frequency response. Just keep a rule of thumb that for every 1A the smallest capacitance should be no less than 1500uF. Dealing with peaking consumption of 3A I'd say 4700uF is the least you can do.

published 10 years ago