12v to 120/220vac inverter
R1 and R2 are 10 ohm, wire-wound, and at least 5 watts. Wattage/cooling should be increased accordingly if you decide to boost up the output. For D1 and D2 you can use any power diode like the 1N4002 to 1N4005.
This particular circuit can be constructed to handle up to 1 KiloWatt (1000 watt). The power output is determined by transformer T1, and power transistors Q1 & Q2. Assume a transformer of about 15A and the chosen transistors of 2N3055 (15A) type, the inverter can supply about 300 watts with the parts shown. If you are good with electronics all you have to do is replace the 2N3055's and T1 accordingly for more output. It is imperative to mount Q1 and Q2 on large cool ribs. If you intend to boost everything up with a couple kilowatts a standard (5") cooling fan will also be required. If this is the case, the 2N3771 power transistor is a good choice at 30Amps. NTE's replacement, NTE181, is an improved version of the 2N3771 and carries 90volts instead of the 40 volts and can dissipate 200W instead of 2N3771's 150W.
It is mandatory to include at least one suitable fuse and enclose this project in the correct casing. To be really safe you may want to include a primary and secondary fuse for your own protection. You are dealing with 120VAC or 220VAC at respectable amperage so be careful. The power cord also needs to be secured to prevent accidents.
The 68uF Tantalum capacitors were chosen for their endurance. Normal electrolytic capacitors would overheat and explode. Some sort of cooling fan inside the project case may be a good choice.
Source: Leksound project
Power Amplifier Class B
Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have big tolerance, so you can build it from any components which you can find at home. The and transistors can be any NPN type power transistor, please do not use Darlington types. The output power is around 60W.
Some comments:
- capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequencies are getting louder.
- capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quieter.
- this is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500? trimmer resistor.
Source: Electronics lab