Function generator

A function generator is a device for generating periodic electric signals of different waveforms, in particular sinusoidal, square, triangle and ramp, with adjustable frequency (usually up to a few MHz) and amplitude.

Function generators used to verify electronic circuits such as amplifiers and filters.

Structure and properties

Depending on the equipment are settings for symmetry, equal share, and often for Wobbelfunktionen available. Some devices contain a frequency counter for accurate adjustment.

Analog function generators

Simple function generators with analog circuitry included an adjustable triangle oscillator whose output signal is brought via a nonlinear circuit in approximate sinusoidal shape. In these devices, the sine outputs i have A. a relatively high total harmonic distortion. The square-wave signal is generated from the triangle by means of a comparator, the pulse width of the rectangle can be set by changing the reference voltage. This structure is in the form of integrated circuits available (for example, XR2206, ICL8038, MAX038 ), making it very cost effective to implement.

Digital Function Generators

Digital Function Generators, which are common today, working with direct digital synthesis (DDS ) and can generate different periodic waveforms. The accuracy is much higher than for devices with analog circuitry and depends primarily on the internal resolution of the DDS from. When the clock source is usually a quartz oscillator which clocks the DDS. About alterable memory tables can also generate arbitrarily programmable waveforms and output periodically with some of these devices. These function generators are referred to as arbitrary waveform generator.

Operation

In the adjacent figure, a simple function generator is shown in analog circuitry. The operational amplifiers OP1 and OP2 generate described the rectangle and triangle signal as in the triangle generator. Resistors R5 and R6, and diodes D1 to D6 form the sine shaper ( sine shaper ), a voltage-dependent resistor. Increases the delta voltage, are first conductive D1 and D2 R5. Then conducting D3 and D4 on R6, and finally also conduct D5 and D6. The higher the voltage across R4, so low-ohmic, the sine - shaper circuit, and the more the voltage divider attenuates R4/Sinus-Former the signal. OP3 is wired as a buffer amplifier with gain = 1.