Using a Basic Function Generator 1.1 2004/04/14 15:38:45 GMT-5 2004/04/14 16:49:51 GMT-5 CJ Ganier seejaie@rice.edu CJ Ganier seejaie@rice.edu Adrian Valenzuela adrianv@rice.edu Patrick Frantz jpfrantz@rice.edu function generator Introduces the purpose of a function generator and explains the use of common function generator controls.

What is a function generator? A function generator is a device that can produce various patterns of voltage at a variety of frequencies and amplitudes. It is used to test the response of circuits to common input signals. The electrical leads from the device are attached to the ground and signal input terminals of the device under test.

Features and controls Most function generators allow the user to choose the shape of the output from a small number of options. Square wave - The signal goes directly from high to low voltage. Sine wave - The signal curves like a sinusoid from high to low voltage. Triangle wave - The signal goes from high to low voltage at a fixed rate. The amplitude control on a function generator varies the voltage difference between the high and low voltage of the output signal. The direct current (DC) offset control on a function generator varies the average voltage of a signal relative to the ground. The frequency control of a function generator controls the rate at which output signal oscillates. On some function generators, the frequency control is a combination of different controls. One set of controls chooses the broad frequency range (order of magnitude) and the other selects the precise frequency. This allows the function generator to handle the enormous variation in frequency scale needed for signals. The duty cycle of a signal refers to the ratio of high voltage to low voltage time in a square wave signal.

How to use a function generator After powering on the function generator, the output signal needs to be configured to the desired shape. Typically, this means connecting the signal and ground leads to an oscilloscope to check the controls. Adjust the function generator until the output signal is correct, then attach the signal and ground leads from the function generator to the input and ground of the device under test. For some applications, the negative lead of the function generator should attach to a negative input of the device, but usually attaching to ground is sufficient.