What Is a Function Generator? Types and Selection Criteria
A function generator is an instrument that produces waveforms such as sine, square, ramp and pulse at a set frequency, amplitude and offset to feed a known test signal to a circuit.
A function generator (function and signal generator) is a test instrument that produces waveforms such as sine, square, ramp, pulse and noise at a set frequency, amplitude and offset. It is used to feed a known input signal to amplifier, filter and sensor circuits, to try out circuits in communication and embedded system development, and for measurements in training laboratories. It produces the signal; you need an oscilloscope to view it and a power supply to feed the circuit.
Types
- Function generator: Produces standard waveforms such as sine, square, ramp and pulse.
- Arbitrary waveform generator: In addition to standard waveforms, produces user-defined or stored custom waveforms. The Unit models in the catalog do both.
- Generator with power amplifier: Adds a built-in power stage to the output and drives a low-impedance load without a separate amplifier (UNI-T UTG1022X-PA, 4 W).
- Multi-channel generator: Channels run independently or locked to each other, for two phase-shifted signals or a four-channel test set-up (UNI-T UTG9354T, 4 channels).
Catalog models
| Series | Model | Sine upper frequency | Channels | Key feature |
|---|---|---|---|---|
| UTG900E | UTG932E, UTG962E | 30 / 60 MHz | 2 | 200 MSa/s, 14 bit; square wave up to 15 / 20 MHz |
| UTG1000X | UTG1022X, UTG1042X | 20 / 40 MHz | 2 | 200 MSa/s, 16 bit |
| UTG1000X | UTG1022X-PA | 20 MHz | 2 | 4 W power amplifier |
| UTG2000A | UTG2025A | 25 MHz | 2 | |
| UTG2000B | UTG2062B, UTG2082B, UTG2122B | 60 / 80 / 120 MHz | 2 | |
| UTG2000X | UTG2062X, UTG2082X, UTG2122X | 60 / 80 / 120 MHz | 2 | 16 bit, touchscreen |
| UTG4000A | UTG4122A, UTG4162A | 120 / 160 MHz | 2 | UTG4122A: 500 MSa/s, 16 bit |
| UTG9000T | UTG9354T | 350 MHz | 4 | 2.5 GSa/s |
Selection criteria
- Upper frequency by waveform: The frequency in the model name is for sine. Square, pulse and ramp waves have lower upper limits; the UTG932E gives 30 MHz sine, 15 MHz square and 400 kHz ramp. If you need a square wave, check the model's square-wave limit.
- Channel count: For a single signal, the 2-channel models are enough. For phase-shifted driving, I/Q or multi-axis tests, choose a model whose channels can run locked and, if needed, a 4-channel model.
- Sampling rate and vertical resolution: The sampling rate determines how smoothly high-frequency arbitrary waveforms come out; the vertical resolution (14 or 16 bit) determines how fine the small amplitude steps are.
- Modulation, sweep and burst: Communication circuits need AM, FM, PM and FSK; filter and loudspeaker tests need frequency sweep; pulse tests need burst mode. Confirm that the mode you need is available on the model.
- Output power: A generator output is meant for a measurement signal. If a load that draws current, such as a coil, a piezo element or a small loudspeaker, is to be driven directly, you need the UTG1022X-PA with power amplifier or a separate amplifier.
Common mistakes
- Forgetting the load impedance setting: If the output is set for a 50 Ω load but connected to a high-impedance input, the amplitude in the circuit is about twice what the display shows. Set the instrument's load setting to the actual load.
- Planning a square wave from the sine frequency: Expecting a 60 MHz square wave from a 60 MHz model; the edges round off or the frequency cannot be produced at all.
Brands in the catalog
All 15 active products in the Function and Signal Generators category are Unit models; price and lead time are given on quotation. To view the generated signal see the Oscilloscopes category, and to power the circuit under test see Laboratory Power Supplies.
Frequently asked questions
Are a function generator and a signal generator the same thing?
In everyday use the two names usually refer to the same instrument. A function generator produces standard waveforms; an arbitrary waveform generator also produces user-defined waveforms. RF signal generators are a separate instrument class for much higher frequencies.
How many MHz does a function generator need?
Start from the highest frequency and the waveform you need to produce. For sine, the model frequency only has to be above your need; for square or pulse waves, check the model's square-wave limit. For example, the UTG932E produces 30 MHz sine and 15 MHz square.
Why is the amplitude on the display different from what I measure?
In most cases it is the load setting. If the instrument is set for a 50 Ω load and connected to an oscilloscope's high-impedance input, the measured amplitude is about twice as high. Set the load to high impedance (High-Z) or terminate the line with 50 Ω.
What is a function generator with a power amplifier for?
A normal generator output provides a measurement signal and its amplitude drops into a low-impedance load. The 4 W power amplifier in the UTG1022X-PA lets you drive loads such as coils, piezo elements or small loudspeakers without an extra instrument.