0
\$\begingroup\$

I've been looking at Piezo drivers lately. They are effectively 0->100v output amplifiers with 0->10v input. Which can source ~60mA, at a few KHz.

The drivers I've seen mostly use high voltage opamps on the output (Apex PA41s for example). However those opamps are very expensive. Is it possible to use a low voltage opamp to provide the feedback to a high voltage MOSFET something like the following schematic?

driveridea

Or is there some other reason to favor a integrated solution?

\$\endgroup\$
  • \$\begingroup\$ You are missing a resistor at the drain side - your Vout == GND at the moment. \$\endgroup\$ – RJR Jun 17 '15 at 0:51
  • \$\begingroup\$ If the MOSFET is ever fully off (or even close to) then you'll fry the amp there. \$\endgroup\$ – Ignacio Vazquez-Abrams Jun 17 '15 at 0:56
  • \$\begingroup\$ Class A would probably be unsuitable - you'd need push pull high voltage MOSFETs, bias circuitry and high voltage level shifting and compensation for the capacitive load. If you can design it and it works the parts will be cheaper than the Apex hybrids. \$\endgroup\$ – Spehro Pefhany Jun 17 '15 at 1:04
  • \$\begingroup\$ LM3900 is a unusual part, but dirt cheap and can interface with high voltages nicely. \$\endgroup\$ – Nils Pipenbrinck Aug 24 '15 at 10:53
1
\$\begingroup\$

Your MOSFET or power suppy would blow up in a flash because as soon as MOSFET input goes high it will connect the 100V directly to ground.

Have a look at the way Australian Silicon Chip Magazine drives its piezos in its "Piezo Transducer boat anti-foul system", design published September 2010.

www.siliconchip.com.au

\$\endgroup\$
  • \$\begingroup\$ The linked article seems to be paywalled for me. \$\endgroup\$ – new299 Jun 17 '15 at 11:12
0
\$\begingroup\$

What topology are you using? If it is voltage to voltage, then you are missing an extra resistor in your feedback from V- to ground.

How are you varying the output from 0 - 100? It looks like a constant output voltage when the MOSFET is on.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.