150v 80Khz piezo driver amplifier

[Dxvideo]

Hi all,

I need a 150Vpp output @ 75-80Khz frequency for a project. I need only 15-20W power at the load. Do you think an IC amp can handle that requirements with a transformer on output?

Thanks in advance..

[pinkmouse]

You firstly need to check datasheets, to see if the chip amps will go that high without roll off.

[Dxvideo]

I already checked LM1875, 1876 and 3886 datasheets; with LM1876 and 3886 there is no problem that they have a bit under 100Khz but LM1876 they only say 70Khz power bandwidth..
But at this point i have a transformer calculation problem.
- First, i dont know detailed trafo calculations,
- Second, the trafo has to be 80Khz tuned
- Third, primary coil must have 8 ohm exact inductive load at 80Khz.
- Fourth, this trafo must handle at least 20W power.
And naturally i cannot calculate a working trafo that can realise that needs!
I know that, here is not place for trafo calculations but may anybody calculate that trafo for me?
Thanks a lot.

[Mushal]

In the following website, you can see a large amount of the power op amp product and the technical documents about the pzt driver using their products.

http://www.apexmicrotech.com

In my experience, their product works well on the pzt actuators.

[Dxvideo]

Yea, i know that products and for final project i will use a PA84 or PB51. But first i cannot buy one of them because they dont sell at small quantities. And i need a quick solution, however i cannot have that chips less than one month even i can purchase samples..

[neutron7]

150v p-p is like +-75 volts right? couldn't you just bridge 2 chips which doubles the voltage swing. the maximum PS of lm3886 is 84 volts . bridged that would give equivalent to +-80v or so

[djQUAN]

is this for a sonar transducer?

I did a similar project before but since it needed only square waves, I used IRF540 fets and IR2112 driver to put 80Vp-p @ 200kHz into the transducer.

[Dxvideo]

No. Its for piezo ceramic motor driver. And i will use a signal generator to change frequency. So the amp must have 70-80Khz bandwidth at least.

2 chips which doubles the voltage swing.

So if i use two LM3886 bridge and feed with +/-38v i can have 38x4=152v swing teorically. Is it? But i guess there is another problem that;
My piezo pads have 65pF capacitance. At this frequency (75Khz) it looks like short circuit from the amp output.. Do you think LM3886s can handle this?

[ashok]

"........At this frequency (75Khz) it looks like short circuit ...."

How ? The reactance for 65pF at 75Khz is over 30 K ohms ! What am I missing ?

Your voltage swing with bridged mode is twice ( x 2 ) and not x 4.
It's power delivered which is x 4 ( voltage squared ).

[Dxvideo]

May be i am mistaken I havent made any calculation! Just a friend said that! Sorry.