"High voltage" linear piezo driver

[jeremy]

Hi all,

I'm on the lookout for a linear piezo amplifier/driver circuit, does anyone know of a good reference for this? I'm specifically not interested in the PWM style ones, I really need it to be a linear amplifier. My requirements are:

0-10v input
BW > 500k, ac coupled is fine as the lowest input signal of interest is 10k
Drive voltage 0 - 60V minimum, but I would be perfectly happy with 60V or however close one can get with a 60V power rail
Drive current less than 20mA, likely less than 10mA

Of course I could live with +/- rails and output as well. Right now I'm looking at a mosfet push-pull stage on the front of an op-amp. Commercial units are for sale all over the place, so I was hoping someone could enlighten me on any tricks here, or perhaps point me to an old service manual which is online 

Thanks!

[uncle_bob]

Hi all,

I'm on the lookout for a linear piezo amplifier/driver circuit, does anyone know of a good reference for this? I'm specifically not interested in the PWM style ones, I really need it to be a linear amplifier. My requirements are:

0-10v input
BW > 500k, ac coupled is fine as the lowest input signal of interest is 10k
Drive voltage 0 - 60V minimum, but I would be perfectly happy with 60V or however close one can get with a 60V power rail
Drive current less than 20mA, likely less than 10mA

Of course I could live with +/- rails and output as well. Right now I'm looking at a mosfet push-pull stage on the front of an op-amp. Commercial units are for sale all over the place, so I was hoping someone could enlighten me on any tricks here, or perhaps point me to an old service manual which is online 

Thanks!

Hi

If the system really *is* AC coupled and 10K to 500K is the bandwidth ... just use a transformer on a very normal amp.

Bob

[f5r5e5d]

sure about the current?

you should give the piezo C, need it to calc the I @ 500 kHz

also the C load can destabilize amps, may want neutralizing/isolating series L||R for many feedback amps

[moffy]

Hi

If the system really *is* AC coupled and 10K to 500K is the bandwidth ... just use a transformer on a very normal amp.

Bob

You would likely run into serious resonance issues as the leakage inductance of the transformer reacted with the capacitance of the piezo.

[jeremy]

Thanks all for your replies. I do realise that the major problem will be the capacitive loading, hence I was hoping there would be a book somewhere on this topic. I don't know the exact current, but you gotta start somewhere and this is a ballpark number I've come up with.

[moffy]

All you need to know is the piezo you are driving and its capacitance. From that you can easily calculate your loading/current. Classic way to stabilise an opamp driving a capacitor is to place a 50 to 100 ohm resistor between them.

[uncle_bob]

All you need to know is the piezo you are driving and its capacitance. From that you can easily calculate your loading/current. Classic way to stabilise an opamp driving a capacitor is to place a 50 to 100 ohm resistor between them.

Hi

Or ... since it's just a capacitor, calculate a matching network to handle the reactive portion of he load.

Since that's never going to be perfect, the normal approach is to match in the top octave and let it look like an open circuit below that. How well that works depends a *lot* on what your device looks like.

Bob