High-voltage, high-frequency amplifier drives piezoelectric PVDF transducer
Finding wide use in nondestructive testing, a high-voltage, high-frequency amplifier drives a piezoelectric PVDF transducer.
Enrique Vargas, Sergio Toral, Vicente González, and Raúl Gregor, Universidad Católica Nuestra Señora de la Asunción, Itapúa Antequera, Paraguay; Edited by Martin Rowe and Fran Granville -- EDN, July 24, 2008
Piezoelectric transducers find use in NDE (nondestructive-evaluation) applications. The PVDF (polyvinylidene-fluoride) transducer has many advantages, including a wide bandwidth and high sensitivity. These transducers require high-voltage and wide-bandwidth amplifiers. The basis of the circuit in Figure 1 is an earlier Design Idea (Reference 1). The operation of the circuits is basically the same, but this one can drive a 2.3-nF capacitive load at frequencies as high as 500 kHz.
In this circuit, an LM7171 op amp from National Semiconductor replaces the LF411, also from National Semiconductor, of the earlier design. The LM7171 op amp has a unity-gain bandwidth of 200 MHz. To further improve the bandwidth, this design’s mirror circuit uses lower-value resistors to increase the current in the transistors, thus increasing the bias current and the power dissipation of Q3 and Q4. To improve thermal stability, this design adds resistors R16 and R17, and, to increase the current to drive the transducer’s capacitive load, this design adds a current driver to the circuit’s output. VCC and VEE are 15 and –15V, respectively, and VH+ and VH– are a maximum of 150 and –150V, respectively.
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Ground reference for piezo transducer drive circuit is wrongly connected to the output is perhaps a srawing mistake.
Piezo transducer drive output directly connecting to OP-Amp input without current control and proyection is not a very good idea.
Shyam Sunder Tiwari - 2008-6-8 17:16:00 PDT -
Its a little lame that you can't put an image of the one circuit in the article. The PDF link is not usable or broken.
Joe Giacomini - 2008-29-7 12:32:00 PDT -
I appreciate the the designideas high-voltage/high frequency driver for the July 24, 2008 issue. It appears there are mistakes in the schematic. I would appreciate a corrected schematic or a description of the changes that should be made.
I would like to thank the authors and the author of the earlier version for this amplifier. I can use the design for my own hydroacoustics testing.
Alan R Wirtz - 2008-28-7 13:46:00 PDT
