Function signal generator is a kind of signal generator, which can generate certain periodic time function waveform (sine wave, square wave, triangle wave, sawtooth wave and pulse wave, etc.) signal, the frequency range can be from a few microhz to tens of megahz. In addition to communication, instrumentation and automatic control systems for testing, but also widely used in other areas of non-electrical measurement.
（1）Function generator with discrete components: usually a single function generator with low frequency, its work is not very stable, not easy to debug
（2）Can be made by transistor, op amp IC and other general devices, more is produced with special function signal generator IC. Early function signal generator IC, such as L8038, BA205, xr2207/2209, etc., had fewer functions, low accuracy, and the upper limit of frequency was only 300kHz, so they could not produce higher frequency signals, and the way of adjustment was not flexible enough. Frequency and duty cycle could not be adjusted independently, and they affected each other.
（3）The function generator with single chip can generate many kinds of waveforms, reach high frequency and is easy to debug. In view of this, the new generation of function signal generator ICMAX038 developed by the American company, which overcomes the shortcomings of the chip in (2) and can achieve higher technical indicators, which is unmatched by the above chip. MAX038 has high frequency and high precision, so it is called high frequency precise function generator IC. In the design of phase-locked loop, vco, frequency synthesizer and pulse width modulator, MAX038 is the preferred device.
（4）The function generator using special DDS chip can generate arbitrary waveform and reach high frequency, but the cost is high. An electrical test signal instrument that produces the required parameters. According to its signal waveform is divided into four categories
① Sine wave signal generator which is mainly used for measuring frequency characteristics, nonlinear distortion, gain and sensitivity of circuits and systems. According to its different performance and use can also be divided into low frequency (20 hz to 10 MHZ) signal generator, high frequency (100 KHZ to 300 MHZ) signal generator, microwave signal generator, sweep and program control signal generator, frequency synthesis signal generator
② Function (waveform) signal generator which could produce some specific periodic time function waveform (sine wave, square wave, triangle wave, sawtooth wave and pulse wave, etc.) signal, the frequency range can be from a few micro-hertz to tens of megahertz. In addition to communication, instrumentation and automatic control systems for testing, but also widely used in other areas of non-electrical measurement.
③ Pulse signal generator, a rectangular pulse generator capable of producing an adjustable width, amplitude, and repetition frequency, may be used to test the transient response of linear systems or as an analog signal to test the performance of radar, multichannel communications, and other pulse digital systems.
④ Random signal generator. It is usually divided into noise signal generator and pseudo-random signal generator. The noise signal generator is mainly used for: introducing a random signal into the system under test to measure the system performance by simulating the noise in actual working conditions;In addition, a known noise signal is compared with the internal noise of the system to determine the noise coefficient.The random signal is used instead of sine or pulse signal to measure the dynamic characteristics of the system.When the correlation function is measured by noise signal, if the average measurement time is not long enough, statistical error will occur, which can be solved by pseudo-random signal.