VA question

[szzuk]

I'm currently using an amp to give my piezo up to 60V and 5Amps, I'd like to switch to a less powerful amp that would be 80V and 50mA. Would that work?

The circuit and piezo work just fine, it operates at resonance (30KHz), with the piezo capacitance matched by an inductor in series to minimise the impedance at the resonant frequency.

Amp - inductor - piezo.

Now measurements of the setup see the current at 5A peak to peak, what I can't work out is if I have to supply 5A from the amp period, or if some of the current is coming from the inductance/capacitance oscillation and I could use the less powerful amplifier chip.

Thanks,

Szzuk.

 

[ericgibbs]

hi,
Do you have a datasheet or link for the piezo.?
and some details of the amp you are currently using.?

 

[szzuk]

The amp is the OPA548. The piezo isn't commercially available it is a prototype, but it is similar to the ones in the link below, it has a capacitance of 2x 600nF is rated at 0-200V with resonance at 30KHz, it is a stack of 35 piezo layers, each layer about 65 microns thick.

http://www.noliac.com/Ring_benders-58.aspx

Regards.

 

[crutschow]

Can you measure the current of the amp directly at it's output?

 

[szzuk]

I got 8A peak to peak as the output of the amplifier, it was measured with a 150mohm resistor. Across the piezo was around 50Vpp, same too the inductor.

I'm also wondering if resonant matching of the piezo and inductor will let me get more than 50V across the piezo, i.e. can I go above the rails.

 

[szzuk]

The purpose of this post is that I actually want to get 100V across the piezo rather than the 60V I now get - more volts is more displacement. I reckon I could use a different chip, I might have one so I'll just put it on a veroboard and try it. Or else I could try some transformers. I was uncertain about the effect of VA, I read up a little, it appears more about efficiency and getting more power output, and I can't go above the rail.