Hi,
We have selected OPAMPs that meet the following requirements.
・ Voltage ± 50V (sine wave)
・ Current 350mA (Peak to Peak)
・ Frequency 300kHz ~ 400kHz
・ Load piezo element (capacitive load_1.5 μF)
I refer to the following circuit described in the DS of OPA454.
Is it possible to drive a load capacity of 1.5uF?
Best regards,
Hiroshi
Hi Hiroshi-san,
OPA454, OPA455 and OPA462 are unable to support the application, see the maximum output voltage vs. frequency in Figure 6-29 from OPA455's datasheet (of Figure 29 per OPA462's datasheet). Both OPA455 and OPA462 have higher operating voltage, BW and slew rate than OPA454.
If you are able to design the piezo load with discrete op amp, you may consider OPA828 with similar complementary transistor pair at the output driving stage, which is similar to Figure 66.
BTW, are you able to drive piezo transducer (±50Vpp) in floating configuration? If you do, then you can reduce the driving amplitude by half, but you will need dual power amp drivers (180 output of phase). In addition, you may open up your op amp selections slightly. With ±50Vpp driving amplitude in sine wave, your op amp will require a minimum 126V/usec in slew rate + BW to drive the piezo load after 1.5uf compensation.
If you have additional questions, please let us know.
Best,
Raymond
HI Raymond-san,
Thank you for your support.
Customer says that the "floating configuration" is OK.
I understand that the circuit configuration is fig.74 at OPA454 Data sheet , is it correct?
However, there seems to be no OPAMP with SR = 126V / us at high voltage.
Please let me know if you have any circuit information or application notes.
Best Regards,
Hiroshi
Hi Hiroshi-san,
The compact piezo transducer driver for the application is limited. There are 3 ways that may be accomplish the driving requirements.
1. Use APEX power amplifier to drive the application, but the cost will be high.
2. Adapter the following floating driving scheme. OPA452 does not have the BW and Slew rate to drive this. OPA828 or high slew rate op amp will work better, but this may be a discrete power amplifier approach as you initially indicated.
https://www.edn.com/programmable-driver-targets-piezoelectric-actuators/
3. Drive a transformer and couple 400kHz driving signal and high current at the primary, and use turns ratio to increase the driving amplitude at piezo transducer's load. Again, this is a discrete approach.
We have limited op amp selections that may meet 2nd and/or 3rd approach. Please let us know if you need further assistant.
Best,
Raymond
