Complentary pair of driver transistors and Vbe multiplier transistor for most Projects in T0-126 package. Alternative choice to the more expensive T0220 package drivers/Vbe transistors. Ideal to use in small to medium audio power amplifier projects.
Project 65 is the fourth in the series of audio power amplifier projects that uses an op-amp in the front-end stage of the amplifier. The CFA-based op-amp input stage is connected to a full complementary hybrid compound feedback pair output stage. Applying a 1KHz 1.84Vpp input signal, the amplifier produces 35.82Vrms across an 8Ω load when connected to a ±56.6VDC power supply rails and a THD of 0.002% as measured by a QA400 audio analyzer. The amplifier sounded powerful enough even though it puts out less than 200watts into an 8Ω load. More details» 
The TDA8950 is a high-efficiency Class D 2-channel audio power amplifier chip. The typical power output is 150Watts per channel with a speaker load impedance of 4Ω. The TDA8950 chip operates over a wide supply voltage range from ±12.5 V to ±40 V and features low quiescent current consumption. For this project the TDA8950 is configured as a mono Full Bridge Class D power amplifier. This configuration was chosen to effectively avoid a strange phenomenon of a typical Class D power amplifier called "pumping effect". The BTL power output is 300watts at 8Ω with ±37VDC PS rails. More details» 
This is another audio power amplifier project in the series that uses an op-amp in the input stage. The prototype is populated with eight 800V/20A/200W NPN power transistors from Fairchild Semiconductor configured in a quasi-complementary output stage topology. These T0-264 packaged power transistors are typically intended in high-voltage color display horizontal deflection circuit applications but performed very well in this project. Initial test results shows that the amplifier is capable of producing a power output of more than 300 watts into an 8Ω load with ±72VDC power supply rails. 
This is another audio power amplifier project in the series that uses an op-amp in the input stage of the amplifier. The complementary 200V 16A 250W TO3-packaged output stage transistors from On Semiconductor are excessively biased about 500mA of current per transistor. The prototype when connected to a ±35VDC power supply rails was able to produce a power output of 50 watts into an 8Ω load with a THD of 0.00186% and a flat 20Hz to 20KHz frequency response as measured by a QA400 audio analyzer. The overly biased amplifier reproduces surprisingly pleasant listening experience. 