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From what you say, these are transducers for ultra-sonic cleaners, they are designed to work in liquid, NOT in air - I suggest you see if they will work in air (and do what you want, I suspect they won't!). Even assuming they will work in air, I doubt they will survive much power? - I imagine they require liquid to keep them cool and to prevent excessive movement?.
 
epilot said:
I am not sure if my op amps will deliver a 30V P-P or not. Here are the opamps I have at the time: LF411N, LF356N
Of course they will have an output of more than 30Vp-p at 65kHz. Use a 35V supply. Look at their datasheet.

Do you think that they can deliver 3A at 30V?
What is 90W for?? The piezo transducer doesn't have any resistance, it is electrically just a capacitor that needs to be charged and discharged with maybe only 100mA from a couple of emitter-follower transistors at the outputs of the opamps. Look at the datasheet for the piezo transducer.

i think a class D power amplifier is the best choice because i want to use both my transducers in parallel with the amplifier, perhaps a class D bridget amplifier is the best choice.
You don't need class-D for such low power. It would be difficult to make class-D switch at a very high frequency. You can use a square-wave at the 65kHz fundamental frequency to save power.
 
Nigel Goodwin said:
From what you say, these are transducers for ultra-sonic cleaners, they are designed to work in liquid, NOT in air - I suggest you see if they will work in air (and do what you want, I suspect they won't!). Even assuming they will work in air, I doubt they will survive much power? - I imagine they require liquid to keep them cool and to prevent excessive movement?.

I want them for bath cleaning,
perhaps it would be better starting a new thread rather than posting the last questions in this thread...
 
audioguru said:
Of course they will have an output of more than 30Vp-p at 65kHz. Use a 35V supply. Look at their datasheet.


What is 90W for?? The piezo transducer doesn't have any resistance, it is electrically just a capacitor that needs to be charged and discharged with maybe only 100mA from a couple of emitter-follower transistors at the outputs of the opamps. Look at the datasheet for the piezo transducer.


You don't need class-D for such low power. It would be difficult to make class-D switch at a very high frequency. You can use a square-wave at the 65kHz fundamental frequency to save power.

Anyway I want to have a high power with the components that i have in my hand

I used TDA1557 for my transducers and used from one output,
it is a stereo class B amplifier:
https://www.electro-tech-online.com/custompdfs/2006/07/TDA1557Q_CNV_2.pdf

It seems it works fine with 12V,do you think it is able to make it bridged to get more power?

By the way I can not understand this:
"You can use a square-wave at the 65kHz fundamental frequency to save power"
 
epilot said:
Anyway I want to have a high power with the components that i have in my hand

I used TDA1557 for my transducers and used from one output,
it is a stereo class B amplifier:
https://www.electro-tech-online.com/custompdfs/2006/07/TDA1557Q_CNV_2-1.pdf

It seems it works fine with 12V,do you think it is able to make it bridged to get more power?

It's already a bridged amplifier, you can't bridge it again!.

By the way I can not understand this:
"You can use a square-wave at the 65kHz fundamental frequency to save power"

All you need to know is a class-D amplifier would be completely pointless for this application. However, this thread is now well down the second page and you've never previously mentioned you're trying to build an ultra-sonic bath!.
 
Nigel Goodwin said:
It's already a bridged amplifier, you can't bridge it again!.



All you need to know is a class-D amplifier would be completely pointless for this application. However, this thread is now well down the second page and you've never previously mentioned you're trying to build an ultra-sonic bath!.

O yes I just found that it is a bridged amplifier..
Do you think that my scope will show near
24V P-P output for each chanel with 12V supply

I said that yesterday I found the New transducers and decide to make an ultrasonic bath, I should started a new thread about that but I don't know what did happen, it was very late when I wrote my last posts and I was very tired so even I forgot to mention the usage of amplifiers...

By the way I think Ultrasonic bath is = ultrasonic cleaning, is not this thrue?!

P.s what "well down" means in that sentence?
 
epilot said:
O yes I just found that it is a bridged amplifier..
Do you think that my scope will show near
24V P-P output for each chanel with 12V supply

Your scope will show 24v p-p across the output, use two probes in differential mode.

I said that yesterday I found the New transducers and decide to make an ultrasonic bath, I should started a new thread about that but I don't know what did happen, it was very late when I wrote my last posts and I was very tired so even I forgot to mention the usage of amplifiers...

By the way I think Ultrasonic bath is = ultrasonic cleaning, is not this thrue?!

Yes.

P.s what "well down" means in that sentence?

It means a good number of posts down the page.
 
audioguru,
Can you draw a circuit used from an opamp like LF411 and emitter follower for my job...
I want to try it out too
 
Here is an amplifier that will drive your piezo transducer.
If fluid is used then the little transistors might melt, so use TIP31 and TIP32 little power transistors instead.
 

Attachments

  • Piezo Driver.PNG
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audioguru said:
Here is an amplifier that will drive your piezo transducer.
If fluid is used then the little transistors might melt, so use TIP31 and TIP32 little power transistors instead.

audioguru,
I made your circuit on beardbord I used a pair of BD139 and BD140 transistors, I have kind of distortion and perhaps harmonics..
I got a very better results using TDA1557.
Don't know but perhaps it is because 1557 is a bridget amplifier and removes or cancels the distortion?
Perhaps we will get better results if we convert your circuit to a bridged circuit?
The reason that I don't want to use from 1557 is that it has a smal kind of distortions too, don't know what is the problem with it, perhaps thats is because it can not handle that freq?!
 
epilot said:
audioguru,
I made your circuit on beardbord I used a pair of BD139 and BD140 transistors, I have kind of distortion and perhaps harmonics!
How can you hear harmonics of 65kHz?? Even bats won't hear it.
I didn't post a low distortion audio amplifier, it is class-B and therefore has severe crossover distortion. It is made for an ultrasonic transducer.
Audio amplifiers use a substantial idle current in their output transistors to operate in class-AB and include the output transistors inside the negative feedback loop for no crossover distortion.
 
epilot said:
audioguru,
I made your circuit on beardbord I used a pair of BD139 and BD140 transistors, I have kind of distortion and perhaps harmonics..
I got a very better results using TDA1557.
Don't know but perhaps it is because 1557 is a bridget amplifier and removes or cancels the distortion?
Perhaps we will get better results if we convert your circuit to a bridged circuit?
The reason that I don't want to use from 1557 is that it has a smal kind of distortions too, don't know what is the problem with it, perhaps thats is because it can not handle that freq?!

As Audioguru says, why are you bothered about distortion?, it's for driving an ultrasonic bath - distortion doesn't matter. If you wanted to reduce the distortion somewhat (but wby?), then connect the feedback to the output of the transistors rather than the opamp.
 
In 1980, a Telephone System made in South Korea was sold by the company I worked for. Many complaints were made by users about its buzzing speaker sound quality. It used a class-B audio amp like I posted but with a slow 741 opamp and included the output emitter-follower transistors inside its negative feedback loop which didn't reduce the crossover distortion much.
I fixed it by cutting the copper and adding a resistor so that the opamp can drive the speaker directly for the 1st volt, then the transistors drive the speaker for louder sounds.
 

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  • Class-B problem.PNG
    Class-B problem.PNG
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