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Waveform Amplifier for Function Generator

Waveform amplifier is a very handy piece of equipment to have in the lab. Most function generator, pulse generator, and arbitrary waveform generator output voltage are limited to about 10V. Function generator output resistance is typically 50 ohm, making it not suitable driving low resistance (high current) load. For applications require higher voltage or higher current or both, a waveform power amplifier is required. For applications require to drive heavy load, the waveform output resistance must be very low (e.g. less than 1 ohm). Similarly some applications require to drive high capacitance, a high power amplifier is needed. The TS200 and the TS250 are high voltage and high current amplifier for general laboratory and bench testing. It can output up to 65V (TS250-7) or can drive more than 6.5A (TS250-0). See our products page for additional information.

Figure 1. TS200 waveform amplifier functional equivalent circuit.

Figure 2 shows how to amplify a function generator to drive heavy load or large capacitance. It uses the TS200 wideband power amplifier. The function generator or pulse generator output is connected the TS200 modulation input. The TS200 output is connected to the load. Typically, the TS200 DC Offset or DC output voltage is set to zero and input modulation is set to DC-couple. For the A-version of TS200 the gain is unity (gain of one). Whatever voltage output from the signal generator is buffered (current amplified) by the TS200. For the B-version of TS200 the gain is 20dB (gain of ten). Voltage at the Mod Input is amplified by a factor 10.

Figure 2. Application diagram showing a signal generator is amplified by TS200 for driving heavy load.

The TS200 modulation output can be AC-couple or DC-coupled. For the B-version, if the TS200 is set to DC-couple, both the DC voltage and AC signal are amplified by a factor of 10. If the TS200 is set to AC-couple, only AC signal is amplified while the DC output is set by the DC Offset knob.

In summary, a function generator produces the desired signal waveform and the TS200 amplifies the signal to drive high current load or high capacitive load. The TS200 amplifier is flexible enough to work with a variety of function generators, pulse generators, and arbitrary waveform generators.

Waveform Amplifier Applications

• Function generator amplifier
• General lab power amplifier
• Piezoelectric Driver
• AC Magnetic field Driver
• Helmholtz coil driver
• Transient response testing
• LDO PSRR measurement

Figure 1 shows the functional equivalent diagram of the TS200 lab amplifier. It features a selectable AC or DC coupled input. It also feature an adjustable DC offset voltage output which is useful for LDO PSRR and line transient response testing. Two versions of the TS200 are available, the A-version has unity gain and the B-version has 20dB gain.

Most function generator and signal generator output voltage are limited to about +/-5V. Their output impedance is also designed for 50 ohm system. These generators expect the load to be 50 ohm too. For test applications required higher voltage, a function generator amplifier is required. As shown in Figure 2, using the TS200/TS250 waveform amplifier and a function generator together formed a high voltage function generator for many of the bench laboratory testing applications. Because the TS250/TS200 waveform amplifier can output up to 70 watts of power, they can also do the job of a high power function generator for heavy loads.

Many research and development laboratory such as those in universities and other R&D facilities often required laboratory power amplifiers that can output high power, or high current, or high voltage, or any of the combination. Examples of laboratory amplifier usages are driving Helmholtz coil (high current), MEMS or microelectromechanical systems (high voltage), pulse and transient thermal generation (high power), driving piezo transducer (high voltage and high current), and much more. The TS200 and TS250 are ideal bench equipment for R&D lab amplifier.

High Voltage Function Generator

Laboratory Amplifier

Magnetic coils are use to produce magnetic field for applications such as scientific experiments, lab test and measurement, magnetic interference, calibration, and much more. To produce high-strength magnetic field, high current is needed. The waveform amplifiers listed in Table 1 below are basically high current function generator amplifier. An example is shown Figure 3 and the waveform amplifier is driving a Helmholtz coil to produce a uniform AC Helmholtz field.

Driving Magnetic Coils

Function Generator Amplifier Connection

Figure 3. The TS250 is acting as high current function generator to drive an Helmholtz coil pair.

Many bench tests and lab experiments uses common signal generator. These signal generation equipment are either weak in output current or low output voltage. Example of such signal is DAQ (data acquisition system). Most DAQ analog outputs can only drive about 10mA and up to about 10V. If the bench testing requires high current signal (i.e. 5A) for driving an AC magnetic coil, a signal generator amplifier is needed to “amplify” the current with or without  amplifying the voltage as shown in Figure 4.

Signal Generator Amplifier

Waveform Amplifier Typical Performance

TS200-0A, 1-ohm load (+/-5A), 100kHz

TS200-0A, 3-ohm load, 100kHz

Figure 5. Using two amplifier drivers connected together will increase the current by two fold.

More Output Current

As shown in the Selection Guide below, the TS200 and TS250 are capable of output very high current from 1.4A to 6A. For some laboratory experiments, even higher current or power is needed. Fortunately two or three lab amplifiers can be parallel connected as illustrated in Fig 5. The total current is the sum of the two waveform amplifiers current combined. The two high-voltage function generator amplifiers must be isolated each with a 0.3Ω to 1.0Ω series resistor. Okay to use higher resistance for higher voltage output. Use high power dissipation resistors to handle the high current.

Table 1. Select a Bench Laboratory Amplifier for Testing

Related App Notes

High Current Amplifier

Lab Amp App Note

PDF Version of this App Note

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Waveform Amplifier Usages

General laboratory power amplifier

University R&D

Scientific and industrial testing

Driving magnetic coil

Piezo motors/actuators

Microscopy

Plasma physics

Optical switches and modulators

Circuit characterization

Electrolytic/Electrochemical cells

MEMS

Automotive transient test

Copyright: Waveform Amplifier for Function Generator

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TS200 Price List

Figure 4. Example of signal generator amplifier producing alternating magnetic field.

Typically our waveform amplifiers is connected to a function or signal generator. Our amplifiers have 50 ohm as well as high-Z input that will work with most function generators. Some examples are shown in Table 2. Our products have BNC connector input which is compatible with most of the generators.

Table 2. Function Generator Selection Guide

Function Generator Selection Guide

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