# Reverse the drain of a Channel - N Mosfet using a P - Channel Mosfet? [closed]

I am working on a school project which consists of converting audio signal into amplified pwm signal with a tda amplifier (raw) not a complete circuit with resistors and capacitors, then converting the pwm pulse to 100% of the power supply voltage, and then interpreted as light with a 24v led strip, allowed transistors are MOSFETs and TDA amplifiers for that convert, obtaining the pwm signal only in the anode(+) of the led, and using the negative as gnd(ground).

The problems doing the basic circuit with TDA2050, IRFZ44N:

1. The wave becomes inverted, why? because the irfz44n reads the positive signal and then releases the negative drain, based on the positive input voltage of the gate in the range of 0v to 10v maximum.

HERE the normal wave (not inverted)

HERE the wave (inverted)

HERE a pwm normal signal

This problem affects not only the wave, it also affects the pwm output, which will be inverted.

1. The pwm signal will go out on the cathode instead of the anode, causing the project to fail.

Now the solution that I formulated to make the pwm output be in the anode (positive) instead of the cathode (negative), consists of using TDA2050, IRFZ44N and L7805CV and irf9540n, here is the circuit:

Explanation: the signal from the left channel enters and reaches the TDA amplifier, the positive on pin 1 and gnd on pin 3, then 24v 1A is fed on pin 5 as positive and on 3 as gnd, then the signal is amplify and become pwm to exit through pin 4 and reach irfz44n through the gate, sharing the gnd in the source, Then the L7805cv feeds the irfz44n with 5v, and then emits the negative pwm signal (drain) to the irf9540n gate, something necessary since the irf9540n has a gate limit of 10v if I'm not wrong, Then, the 5v that power the irfz44n are joined with the 24v in the source of the irf9540n to complete the voltage of the irfz44n (5v) and to be able to drop (drain) of 24v pwm in the anode (positive) of the led strip.

My questions are:

1. Can L7805CV be damaged by joining its positive output voltage (5v) with the positive power supply voltage (24v) as it is mentioned in the picture(5v and 24v join)?

2. Is my circuit at risk of a short circuit?

3. Does my circuit have the risk of damaging the 3.5mm audio input or any device in which I test it with some 24v or 5v overvoltage due to these combinations of mosfets?

4. What suggestions do you give me, in case something else is needed or something is wrong in my circuit?

A small note, I managed to do this only with the tda2050 and the irfz44n, with 5v of voltage, but it was only a test, not something permanent for the aforementioned not works in anode only in cathode and i want to include 4 amps more or 2 that these mosfets and transistors and amplifier allows me...

More explained schematic added:

• TDA2050 does not do PWM, so can you clarify why you mention PWM.? – bobflux May 2 at 13:53
• but as i know irfz44n needs pwm to work That's not true, the IRFZ44N is "just" an N-channel MOSFET, it doesn't dictate how one should use it. I can for example use it to switch on/off a motor without using PWM. – Bimpelrekkie May 2 at 14:15
• To me it looks like you want to do things that are too complex for your skill level. A TDA2050 is completely unsuitable for this. I suggest that you search the internet for projects that do something similar to what you want and then re-build the same. If you continue with what you're doing above you will end up with damage comonents and lots of frustrations as it isn't going to do what you want this to do. – Bimpelrekkie May 2 at 14:15
• PWM is a pulse modulation, it means a pulse I knw what PWM means, no need to explain it. that human can't perceive Oh but this human can use an oscilloscope so I can observe a PWM signal. Your talking about the "circuit" is confusing and confused. I might comment more after you have included a proper schematic replacing that "hookup" what you show now. Circuit designers communicate using schematics. – Bimpelrekkie May 2 at 14:57
• So far, this question appears to be a train wreck. Too many assertions about chips that are wrong and too much guesswork to try and figure out what you are actually trying to do. Gather your thoughts, explain what you are trying to achieve, explain what the given input is and what the output signal needs to be. Don't make half-baked suggestions that a TDA250 produces a PWM output and no need to show a diagram of what an inverted sinewave looks like. Focus and then focus some more. – Andy aka May 2 at 15:11

I'm sorry to have to tell you, but you're in way over your head here.

1. "Can L7805CV be damaged by joining ... ?"
• It's certainly possible that this will damage the 7805, but even if it doesn't you can't 'share' a single wire and have both 5Vdc and 24Vdc on it at the same time. Not "it's not a good idea", but "it's physically impossible".
1. "Is my circuit at risk of a short circuit?"
• From what you've shown, there isn't anything obvious there which would result in the traditional definition of a 'short circuit'. That doesn't mean that your circuit will work though.
1. " Does my circuit have the risk of damaging the 3.5mm audio input ... ?"
• Unless something goes wrong with the TDA2050, or you deviate from this circuit in some way, then no there doesn't appear to be a significant risk of damaging whatever you plug in at the input.
1. "What suggestions do you give me, in case something else is needed or something is wrong in my circuit?"
• where do I start ... There is nothing in your circuit which actually works the way you think or hope it works. Literally nothing.

Starting from the left:

• The TDA2050 is an Analog audio power amplifier. It does not produce a PWM output. The datasheet is here - does your circuit look anything like the 'Test and application circuit' on page 1? No, it does not. You haven't even connected all of the pins, nevermind connecting them in the way they need to be connected. But since you want to use a single 24Vdc supply, skip over to page 6 and look at the 'Single-supply typical application circuit' - it has some extra parts to make it work, and your circuit doesn't look anything like this either.
• The IRFZ44N (datasheet) is a power N-Channel MOSFET. It doesn't 'need' a PWM signal to work. It can work with a PWM signal, but can work just as well with an analog signal - depending on the way it's used in the circuit. As you can see in the datasheet, the maximum Gate-Source voltage (Vgs) you should apply to it is 20V. The way you've got it connected to the output of the TDA2050 makes it likely that it could see almost 24V out - this will damage the TRFZ44N. But even if you were driving the IRFZ44N correctly, it would not produce a useful output for you in the way you have it connected. In the way you have it, the IRFZ44N behaves a lot like a switch, opening and closing the 'connection' between its drain and source pins - so there is no way for it to ever produce a 'high' (either 5Vdc or 24Vdc ) output at its source pin. It will either be 0V/Ground or Floating/Open-circuit.
• The L7805CV will not do anything useful in the way you have it connected. You've shorted it's input and output together, and your purpose for doing this is not entirely clear. You seem to expect that this will somehow provide both 5Vdc and 24Vdc simultaneously over the same wire. It won't. It's not physically possible, no matter what voltage regulator you use. It's also not clear why you would even want to do this.
• The IRF9540 P-Channel MOSFET will not do much of anything useful in the way you have it connected here. The signal you're feeding its gate (either 0V/Ground or Floating/Open-circuit from the IRFZ44N) will (similarly to the IRFZ44N) violate the maximum Vgs of the part (20V) - causing it to be damaged. Even if it does continue to 'function' in some way for a while before dying it will never ever switch off because the signal in its gate never goes 'high'.

You need to start over from scratch with this and clarify what your requirements are for the circuit so that you can do some research into appropriate parts and the way to use them.
The parts you've chosen to use, and the way you're trying to use them, are completely unsuitable for achieving what you say you're trying to do.

• Before of select your answer as best, because it are really good, i will ask little things about your answer ... – RylerMcCutchen May 2 at 15:48
• It was clear to me that the 7805 would be damaged, could a diode block the 24v, to prevent that damage on the positive output of the 7805? Or would it cause a short circuit in said line? – RylerMcCutchen May 2 at 15:53
• Could a diode block the 24V from the 5V net to prevent damage to the 7805 ... ? Yes it could. but it's unlikely that this would have much (if any) positive improvement to your circuit. As a whole it still wouldn't work. – brhans May 2 at 16:29
• The last question, exist a way to obtain analog negative from tda2050? instead positive? pin 4.. – RylerMcCutchen May 2 at 16:32
• @RylerMcCutchen Yes, give it a bipolar power supply instead of just a single-ended one. But you have much deeper problems than that--for one thing you don't even have anything connected to the inverting input! – Hearth May 2 at 16:43