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# Electronics and Electrical Engineering Design Forum

## How can I amplify a 100khz signal to drive a piezo

I want to be able to amplify a 35khz to 100khz signal to power a piezo transducer to create cavitation in deionized water for cleaning. Will regular audio power amps work for this? Voltages in the 50 to 150 range are needed to drive the tranducer which has approximately 10 ohm impedance.

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3 years ago

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Hmmm …

… 150 Volts, 10 Ohms …

… that’s 2.25kW – are you cleaning or cooking!

Joking aside – what are the actual drive voltages you expect to use?

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Some one has worked this out at last !!

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Normally 100 watts per gallon of fluid. So 40 gallon tank will neet 4000 watts of power for normal operation.

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Ahh yes perhaps I was a bit off in my estimation of impedance. At resonance the impedance will look similar to this chart. I am actually building a Langevin from scratch with a different design than is common. I am trying to overcome some common problems with Piezo drive Ultrasonic cleaning systems currently in use. I am new to this game and am just trying to gather components for testing and such. I have not even received my new scope or the components to build a function generator yet. This is cool stuff you guys play with.

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I forgot to mention, each transducer in a cleaning system uses 40 to 75 watts of power. All I read on Langevin transducers tell me it takes hundreds ov volts to get them to resonate at frequency.

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Nice little circuit here halfway down the page for ultrasonic bath

http://www.repairfaq.org/sam/samschem.htm

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Thanks Mark, this is pretty simple.

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No worries welcome

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Regular audio amps are probably more tailored for audio than 35-100KHz. When I was working on driving large piezo elements, we would use a square wave into a power transformer. Note the inductance of the transformer and the capacitance of the piezo form a tuned circuit which helps you in two ways: it filters the square wave drive into a fairly nice sinusoidal drive at the piezo, and amplifies the voltage at the peizo based on the Q of the tuned circuit. We typically put known resistance in the path to better control the Q, at the expense of some power loss.

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Thanks, I’m looking at transformers now. I might be able to scale up a version of the circuit Mark found for me. What is Q?

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Thanks Todd, I had no idea.

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Many audio amps will not like running full bore at 35 kHz to 100 kHz. They might run fine at reduced power.

Based on the plot you supplied the load Z is 500 ohms and you want to supply 50 watts. An 8 to 500 ohm transformer connected to a 200 watt, 8 ohm audio amp just might work. But where to get such a transformer?

The Hammond 1650 WA transformer might be worth a try. It is rated for 280 watts, 1900 ohms to 4-8-16 ohms and full power up to 30 kHz. \$323 at Digikey.

http://www.hammondmfg.com/1608A.htm

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