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TS200 piezoelectric driver for driving transducers and actuators. TS250 piezo driver for driving piezoelectric transducers.

Piezo Driver

High-current piezo driver is perfect for driving high capacitance and high frequency piezo transducers. Piezoelectric transducers and actuators are highly capacitive devices. Because of their large capacitance, their overall impedance is relatively low at higher frequencies. In addition, these piezo devices often require high voltage, 20Vpp to 60Vpp or higher. The combination of high frequency and high voltage requires a high-current piezo driver. Figure 1 shows the high-frequency, high-current piezoelectric driver connection and setup.

Figure 1. The wideband waveform amplifier is used for high frequency piezo driver.

Calculating Piezoelectric Driver Current

Piezo Driver Connection

Piezo transducer is driven by the TS250 High-voltage piezoelectric driver.

Table 1. High frequency piezo driver Selection Guide

The second type of piezoelectric elements require the highest peak voltage possible and usually positive voltage only. Such examples include PZT motor and stage, actuator and stack, bimorph, etc. These type of transducers general require a voltage range from 0V to a maximum positive voltage (i.e. +60V) and no negative voltage. Use Table 1 to select a unipolar piezo transducer driver.

Connect two piezoelectric driver amplifiers in parallel for high output current

Figure 3. Parallel two piezo driver amplifiers increases the output current by 2x, or increase power by 4x.

Note 1. Piezo element is capacitive which means their power is reactive. The TS250 output current is adjusted for reactive power.

Note 2. Peak resistive current is specified at maximum voltage minus 1V. For exmaple 19V for the TS250-1.

High Power Piezo Transducer driver Use Multiple Units

Our high power piezo transducer driver are able to output high current and high voltage, thus high power.  To further increase the piezo driver amplifier output power/current, 2 or three or more units may be parallel connected. To do so, each PZT transducer driver is isolated from one other with a series resistor as shown in Figure 3. Typically the resistance is between 0.5 ohm and 2 ohm. However, the series resistor may be uses as resistive matching. In that case, the resistance may be increase to higher value as discussion in the previous section "High Frequency Piezo Driver Impedance Matching".

Most piezoelectric (PZT for short) actuators/transducers require higher voltage than most signal generator can supply. For example, a PZT transducer drive voltage is typically more than 10Vpp and the voltage can easily require up to 100V or higher. Most available function generator output voltage are less than 5V into 50 ohm load. Such low voltage is not enough to drive piezoelectric elements. Thus a high current, high frequency, and high voltage piezo driver amplifier is required. For example, a pzt motor needs a 40Vpp pulse waveform to operate, but most signal generator can only output 5V or less. Already depicted in Figure 1, the driver amplifies the signal from the function generator and outputs high voltage yet high-current waveform to drive the piezo device. In short, the wideband amplifier/driver is ideal for driving pzt motors, actuators, and transducers.

 I=V/Z=V/|1/jωC| =ωVC=2πfVC


The current required to drive the piezo transducers is determine using Ohm's law. The piezo element current is proportional to the frequency, voltage, and capacitance as in Equation 1. From Equation 1, V is the voltage, I is the current, C is the piezoelectric capacitance, and f is the frequency.

High Voltage and Power PZT Driver

Using a resistor to impedance match the high frequency piezoelectric driver.

Figure 2. Using a series resistor to increase the piezo driver amplifier output current and power.



High power piezo transducer driver using external voltage supply.

Piezo motor driver

Power amplifier for function generator

High power function generator

Laboratory power amplifier

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As an example, for a high-frequency PZT actuator with a capacitance of 1uF, the peak-to-peak voltage needed is 20Vpp, and 100kHz frequency, the required peak-to-peak current is 12.6App (or about 6.3A 0-to-peak). Therefore the high frequency piezoelectric amplifier driver must be able to output high current. If the frequency is higher or the required voltage is higher, the required current is even higher than that. In short a high current driver is needed for high-frequency pzt applications. Note the current is reactive current. See the Reactive Power section below for more details.

Determine Voltage Requirements

It is crucial to understand the required voltage for proper piezoelectric transducer operation in order to select the optimal PZT driver amplifier. This usually involve careful understand the piezoelectric device voltage specifications. There are generally two types of voltage requirements: bipolar and unipolar.


PZT devices that requires a given peak-to-peak voltage, regardless of positive or negative voltage, is best to use a bipolar piezo transducer driver. Examples of such transducer/sensors are pzt speaker and buzzer, ultrasound transducers, ultrasonic washing and cleaning, etc. These type of PZTs only response to total signal amplitude from the least voltage to highest voltage, whether is positive or negative voltage is unimportant. For example, a pzt element need 60Vpp uses the voltage from -30V to +30V. Use Table 1 below to select a bipolar type pzt driver.


Determine the Power Drive Requirement

Capacitive PZT Devices:

Most PZT transducers are highly capacitive, some actually resistive at the resonant frequency which will discuss in the next section. For capacitive PZT devices, it only require the piezoelectric driver to output a voltage amplitude as discussed above. It does not care about current or power. However it require certain amount of current to drive it at the desired voltage and frequency. The current requirement was discussed above in Equation 1. The higher the frequency, capacitance, or voltage, or any combination, the higher the current is needed. The power required for driving capacitive type PZTs are reactive. This means no power is absorb by the sensor/transducer. All power are dissipated in the driver itself in the form of heat. See Impedance Matching section below for further details.

Resistive Device Type:

The second type of PZT-devices whose impedance becomes resistive at the resonance frequency. These type of piezoelectric elements specify the output power and its resistance at resonant. The type of elements include piezo horn and ultrasonic cleaning transducer. The typical resonant frequency is 40kHz, but some at 35kHz while others are at 80kHz, 120kHz, etc. High frequency piezo driver is needed to drive these devices. Their power range from a few watts to well over 100 watts. See the below section "Optimize Power for Resonance Piezo Transducers" to select a driver amplifier for resonance devices.

High Frequency Piezo Driver Impedance Matching

Reactive Power vs. Real Power

The above section discussed most high-frequency piezoelectric elements are capacitive in nature (except for resonant type). For that reason its impedance is mostly reactive and with very little or no real resistance. These PZT transducers dissipates no real power, but reactive power. Reactive power means all of the power are dissipated in the inside of the high frequency piezo driver in the form of heat. That is, the piezoelectric transducer driver gets hot, not the transducer itself. Our high power piezo transducer drivers can handle the heating power from about 50 watts to over 100 watts (future products). See the below section for techniques to parallel connect two or more pzt drivers to output higher power, real or reactive.

Piezo Driver Amplifier Resistive Matching

One way to reduce the piezoelectric driver self-heating is to make the actuator/transducer more resistive. The simplest way is to add a series resistor as illustrated in Figure 2. This way the resistor will absorb of the power and heats up. The chosen resistance should not increase the overall impedance much. A resistance of 0.25Z to Z is appropriate. Z is the impedance of the high-frequency piezoelectric transducer. For instant, if the pzt actuator impedance is 30j-ohm at 20kHz, the series resistance should be between 7 ohm and 30 ohm. Equation 2 calculates the overall impedance. At 0.5Z, the overall impedance is increase only by about 12%. Additional the matching resistor power dissipation is formulated in Equation 3 below. The power may be high and the resistor may be hot. The series resistor be able to handles the power. Also choose a low inductive resistor type, especially at for high frequency operation.

Resonance Piezo Transducers Driver

As discussed above some PZT elements are resonate at a frequency. At resonance it becomes resistive as opposed to capacitive. Langevin ultrasonic transducer and piezo horn are examples of these devices. The common applications include ultrasonic cleaning and washing, levitation, and vibration. The most common resonant frequency is 40kHz. These resonance PZT usually specify its power rating and a resistance range. They don't normally specified the voltage range. As an example, an ultrasonic transducer spec sheet indicates its resistance range is 15-20 ohm and 40W maximum power. Unless otherwise noted, the power rating is assumed RMS (root-mean-square). Use Equation 4-8 to calculate the power, current, and voltage.

Use Equation 4 - 8 and the below steps to find the optimal high power piezoelectric driver. Start with bipolar amplifier drivers in Table 1.

Equations for resonant piezo driver.






TS200 Selection Guide Piezo Transducer Driver Selection Guide

Stepe 1: Using Equation 5 to divide the driver maximum peak voltage by the transducer's specified maximum resistance. This is the PZT's maximum current. Make sure the PZT current is still within the driver's specified peak current. If the PZT current is higher than the amplifier specified maximum current, then use the amplifier's max peak current instead.

Step 2: Use Equation 6 to calculate the peak power. The current is calculated in Step 1. The resistance is the maximum specified resistance from Step 1. This is the peak power. Use Equation 8 to calculate the RMS power.

Step 3: Repeat Step 1 and Step 2 with the minimum pzt specified resistance.

Due to the piezoelectric transducer specified resistance is in a range, the optimal maximum power driver for the maximum resistance may be different from the driver for the minimum resistance. In this case you may choose the one with the highest voltage, because you may parallel connect two piezo amplifier drivers to obtain higher power as shown in Figure 3.

Let's use the below example. A PZT ultrasound transducer is specified with resistance range of 15 to 20 ohm at 40kHz resonance frequency. Using Step 1, maximum resistance of 20 ohm, and Table 1, the calculated peak current is 2A using the TS250-3 ultrasound amplifier which is within the 2.5A peak current. The Step 2, the peak and RMS power is 80W and 40W, respectively.

Using Step 3 to repeat the calculation using the 15 ohm minimum resistance. The maximum current is 40V/15ohm = 2.67A which is higher than the maximum 2.5A current.  So 2.5A peak current is used.  The peak and RMS power is 93.75W and 46.9W, respectively.

Advance Techniques

High voltage amplifier piezo driver

If the piezoelectric device requires unipolar (only positive) voltage, Figure 4 below uses a DC bias voltage to obtain voltage up to 80V while can output high current at operating at high frequency. For instant, an actuator requires a sinewave voltage from 0V to 80V. Using the circuit in Figure 4, the isolated DC voltage supply provides the bias while the waveform power amplifier TS250 provide the 80Vpp signal. Using this method, the PZT driver able to produce high current and high power (reactive or real), up to peak power of 200 watt (2.5A * 80V = 200W).

Figure 4. This setup forms a high voltage amplifier piezo driver that can output up to 80V and 200 watts.

Important notes for the setup in Figure 4. The TS250 high voltage piezo driver's negative output terminal must be connected to the ground node. The ground node must be common with the function/signal generator ground as well as the pzt element. DC supplies have internal capacitors already. It is still required to add external capacitors for bypassing. This is particularly important for high frequency piezo elements. Multiple capacitors parallel connected is recommended. It is important to use ceramic capacitors with low ESL and ESR. Other capacitor types, such as tantalum and electrolytic may be acceptable. Total external capacitance must be high enough so that its impedance is lower than the piezoelectric impedance. Important note: Do not accidently short the piezo device (load). By doing so is equivalent to connect a negative 80V to the TS250 output which will cause damage!

Transformer Boost High Voltage

Another technique for boost higher voltage is using a wideband transformer. As shown in Figure 5 the transformer turn ratio is 1:N. The secondary-to-primary turn ratio should be in the range 2:1 to 8:1. Iron core transformer is acceptable at lower frequencies, but ferrite core should be use for high frequency to minimize loses. The size of the transformer need to able to handle the intended power level. The wire resistance also need to low enough to minimize loses. The series connected capacitor is recommended to filter any DC offset voltage coming from the high voltage amplifier piezoelectric driver. The capacitance should be larger enough so that the impedance is low enough at the operation frequency. The impedance should be smaller than the transformer's (or in the range of) primary coil resistance. Multiple capacitors connected in parallel is acceptable. Caution: transformer output may be high voltage and hazardous. Must use safe high-voltage handling techniques.

High voltage amplifier piezo driver using transformer to boost the signal.

Figure 5. Using transformer to boost the voltage to over 200V.