Fdb7045l Mosfets

[Tekko]

What can these babies be used for ? I have atleast two that i gonna rescue from an old motherboard.


Datasheet

I was thinking about a primitive class D amp.

[richie00boy]

To be honest, with only two MOSFETs available and any project requiring many more other parts, it's not worth making up a project just for these.

[Tekko]

The most primitive (simple) class d a is a triangular wave oscillator, a comparator, the output fets and a filter.

Why would you say i dont have any other parts ?

[richie00boy]

I didn't say that at all. What I was saying - to use an analogy - was that why decide what car to build when you only have two doors? There are more important components to consider and obtain.

In a class-d amp, I would consider the comparator/op-amp and inductor to dictate the design strategy/implementation of the amp.

[Tekko]

A TL061 as input and to get a NFB loop, a LM339 for oscillator and comparator and a Hex inverter to invert the signal to one of the two fets as they are both NFET would be the main components. The LC filter could be the output filter from a puter ps, just trim the triangular wave oscillator so the operating freq matches the filter and it shoud work, atleast in my theory.

You are welcome to suggest ideas. This would be alittle like the UcD class D, no ?

I was thinking something like this:

[richie00boy]

The inverter you propose won't work as it has no level shifting.

The circuit is not that much like UcD.

It's funny how on that datasheet company webpage, they want to charge you for it, but if you go to Fairchild website which is linked on their page, you can download it for free.

[Tekko]

I have the datasheet for the fets. The link is to alldatasheet.com which is a free datasheet site.

How do you mean the hex inverter wont work ? It sure will invert the signal to the upper fet.

[richie00boy]

It will invert it yes. But not at the correct DC potential. Also the comparator is an open-collector so will need a pull-up resistor. TL061 is a poor choice.

I suggest you do some further reading and think about the voltages required at certain parts of the circuit before continuing

[Tekko]

I said its a basic schemo to have as ground base. I dont always draw out components that has to do with open collector, such things are usually integrated in pspice models.

I have never built a class D amp but i do have knowlege about analog and digital circuits so no need to treat me like a fool.

The inverter may not be a regular hex inverter, but something that can swing between 0v and up to the voltage needed to saturate the switching fets. The FETS i gonna use are logic level gate.

[richie00boy]

Calm down. I'm not treating you like a fool, just trying to offer useful advice.

If you had said your schematic was a concept then I would have reacted differently. I think you will find pull-up resistors actually NOT integrated into models. And how was I to know your inverter was a complex inverter with level shifting? You actually stated it was a "Hex inverter" which is most certainly not the appropriate component. If you don't explain things or use incorrect terminology you have to accept that people will take them at face value or want to correct you.

Have fun. Next time I'll just keep quiet and let you build a fire