Power Requirements / Open Loop Frequency Response
The Latest Information on Piezo Drivers and Controllers
In order to achieve minimum distortion of the output waveform, it is important to reduce the control input amplitude at higher frequencies with the same ratio the output voltage drops. Example: The E-503 (E-663) amplifier can drive a 23 µF load at 100 V peak-peak (sine-wave) up to approximately 15 Hz. At higher frequencies the output voltage drops off, e.g. to 80 V at 20 Hz. Therefore it is important to reduce the input voltage amplitude to 8 V (gain = 10) at this frequency. Otherwise the amplifier will output a clipped sinewave.The frequency response of a given amplifier depends on the amplifier power, the amplifier design, and, of course the Piezo capacitance. For dynamic applications, PZTs require high charge and discharge currents. Those requirements are best met by power amplifiers that can source and sink high peak currents. The average current is of secondary importance. For exact information on maximum operating frequency with a given Piezo load refer to the individual frequency response graphs.
Open loop frequency response data for all PI Piezo Power Amplifiers in this catalog were taken after 15 minutes of continuous operation (Piezo and amplifier) at room temperature. After power up (cold conditions) maximum operating frequency is higher. The indicated capacitance values are small signal values for real PZTs (measured at 1 V, 1000 Hz, 20° C, no load). The capacitance of Piezo ceramics significantly changes with amplitude, temperature, and load, up to approximately 200% of the unloaded, small signal capacitance at room temperature. Therefore the frequency response graphs actually reflect a higher load to the amplifier than the capacitance values indicate.
