help! in need 10 watts (or more) audio amplifier schematic transistor based

[Cluene]

Hi, I'm an electronics engineering student and we have a project in school to make an amplifier (transistor based), I have tried making one but I have already failed two times. I keep frying my transistors (MOSFET). I have resolved to search for a new circuit. Your help is greatly appreciated.

 

[cowboybob]

Can you supply us with a schematic (with component details) of what you've done so far?

That would help. No need to reinvent the wheel or trash everything you've already done.

 

[audioguru]

There are thousands of good audio amplifier circuits on the internet. Most are almost the same.
Show your schematics so we can help you fix them.

 

[Cluene]

Can you supply us with a schematic (with component details) of what you've done so far?

That would help. No need to reinvent the wheel or trash everything you've already done.

This is the schematic of what I have done so far...

https://www.circuitstoday.com/mosfet-amplifier-circuits

 

[Cluene]

the ones that usually fry are the MOSFET's (my classmates' MOSFET fried up too)

 

[Cluene]

yes i'm searching, but right now i'm for a schem that is more affordable with all the expenses that was already spent. perhaps I could find a circuit that uses purely BJT transistors and no FET coz its kind of expensive.

 

[Cluene]

I found this circuit, but its missing component values for C2 and C1

**broken link removed**

 

[alec_t]

The designs you linked to in post #4 are very likely to destroy the FETs if their turn-on voltages are small and the bias adjustment is not set accurately when power is first applied to the amp. In that situation high current flows through both.

 

[crutschow]

I found this circuit, but its missing component values for C2 and C1

**broken link removed**

C1 and C2 are selected for the low frequency response required. I see no value for R1 and R2 also.

Which of the circuits shown in your post #4 reference did you build. There is more than one shown.

 

[Cluene]

The designs you linked to in post #4 are very likely to destroy the FETs if their turn-on voltages are small and the bias adjustment is not set accurately when power is first applied to the amp. In that situation high current flows through both.

Thank you for that information . Pardon me for my ignorance, im really just a beginner in these field and thus need ample amount of guidance. I would like to ask if this could also cause a short circuit? We have also observed that whenever we connect our circuit to a power supply, the indicator for a short circuit will always light up.

 

[Cluene]

C1 and C2 are selected for the low frequency response required. I see no value for R1 and R2 also.

Which of the circuits shown in your post #4 reference did you build. There is more than one shown.

would that mean that the value placed there wouldn't be critical? I have built the 18 watts mosfet amplifier

 

[Cluene]

By the way, just an additional information, we are tasked to make a stereo amplifier. We doubled the "18 watts MOSFET amplifier" (link in post #4). Made all grounds common.... and... is it a good idea to also connect the input audio (positive) as common terminals or we should separate them?

 

[alec_t]

is it a good idea to also connect the input audio (positive) as common terminals or we should separate them?

If you connect them then you've effectively got a mono amp, not a stereo one!

 

[audioguru]

The 10W Mosfet amplifier has C3 connected wrong. Its (-) wire should connect to the positive wire of C4 so that it "bootstraps" R4.

If the bias adjustment pot is set at a low resistance then the Mosfets will not be turned on and will not burn. It is adjusted for an output bias current of maybe 40mA which will not cause the Mosfets to burn unless their heatsink is not big enough.

The transistors amplifier is extremely simple and old. It uses C1 to "bootstrap" R1 and R2.

The value of audio coupling capacitors is simply calculated with the lowest frequency you want. 1000uf will cause the output power to be half (-3dB) at 20Hz into an 8 ohm speaker.

www.redcircuits.com has many audio amplifier projects.
www.sound.westhost.com/index2.html also has many audio amplifier projects.

 

[gary350]

What are the rules of the project?

Did your teacher say, build a transistor amplifier with any transistor you like? If so try an LM3886 transistor. Parts required 9. You will need a heat sink and a DC power supply. This audio transistor puts out 68 watts. 28 volts = 38 watts to an 8 ohm speaker. 35 volts = 50 watts to an 8 ohm speaker. 94 volts max. If you do a web search for LM3886 circuit you will find several.

Look at how small it is. **broken link removed**

Or is this a project where your required to look the transistor specs up in a book and design your own circuit that works?

 

[daGenie]

Hi, I'm an electronics engineering student and we have a project in school to make an amplifier (transistor based), I have tried making one but I have already failed two times. I keep frying my transistors (MOSFET). I have resolved to search for a new circuit. Your help is greatly appreciated.

have tried connecting heat sinks?

 

[audioguru]

The students are learning how to copy an amplifier designed by somebody else. They are also learning how to connect the parts together (Breadboard? Soldering?)

 

[Cluene]

What are the rules of the project?

Did your teacher say, build a transistor amplifier with any transistor you like? If so try an LM3886 transistor. Parts required 9. You will need a heat sink and a DC power supply. This audio transistor puts out 68 watts. 28 volts = 38 watts to an 8 ohm speaker. 35 volts = 50 watts to an 8 ohm speaker. 94 volts max. If you do a web search for LM3886 circuit you will find several.


Look at how small it is. **broken link removed**

Or is this a project where your required to look the transistor specs up in a book and design your own circuit that works?

Our teacher told us to make a stereo amplifier (transistor based for midterms and op-amp for finals).

For the midterm project, we must use a transistor ... it can be either BJT or MOSFET (how many used will not matter), we can also use an IC but I don't think it would be the one used for op-amps (I actually need to clarify this with our teacher). Thank you for the link I'll ask our instructor if we could use it for our midterm project.

 

[Cluene]

The students are learning how to copy an amplifier designed by somebody else. They are also learning how to connect the parts together (Breadboard? Soldering?)

Haha we certainly are learning to copy other people's designs. And yes, we are learning both bread boarding and soldering

Unfortunately, we have yet to fully understand the use of the transistor thus explain out disastrous fate and design piracy.

 

[Cluene]

have tried connecting heat sinks?

Yes we have