High Amplitude Arbitrary/Function Generator Simplifies Measurement in Automotive, Semiconductor, Scientific and Industrial Applications Application Note
Figure 12. AFG3011 Sweep Mode Display.
Figure 13. AFG3011 Pulse Mode Display.
To measure the bandwidth of the amplifier, configure the function generator in sweep mode, select amplitude, start and stop frequencies, as well as the sweep time according to your design specifications. The Tektronix AFG3011 allows convenient access to these parameters via designated short-cut keys on the front panel, and top level screen menu selections. The large display of the generator shows all relevant settings including the amplitude and a graphical representation of the waveform at a single glance, providing full confidence in the instrument settings. An oscilloscope that is triggered by the generator at each start of the sweep traces the amplifier response.
As another measurement example, let us consider the determination of the amplifier's rise time. The latter provides a measure of the amplifier's capability to detect narrow peaks in the measurement signal from the TCD as they are generated by trace amounts of the sample in the carrier gas. The meas- urement setup is the same as depicted in Figure 11, except that the trigger line is not required. The arbitrary/function generator is configured to generate pulses. Modern digital oscilloscopes measure the step response of the amplifier and provide a direct reading of the signal rise and fall time via automated measurements.
On the measurement trace on the oscilloscope screen, use a horizontal marker to find the -3 dB amplitude level which is equivalent to 70.71% of the peak value. Then, while observing the measurement trace on the oscilloscope screen, narrow the sweep range by adjusting start and stop frequencies on the signal generator until the measurement trace starts at the lower bandwidth limit and ends at the upper bandwidth limit. The amplifier bandwidth can then be determined by reading the last settings of start and stop frequencies on the signal generator.
Modern arbitrary/function generators like the AFG3011 allow the generation of signal amplitudes up to 20 Vpp into 50 Ohm loads directly without the use of an external boost amplifier. This simplifies the test set-up and reduces equip- ment cost in many applications. It also saves measurement time, because the generator shows the effective amplitude directly on its display, making a separate measurement with a voltmeter redundant.
Beyond the test applications described in this note, high- amplitude arbitrary/function generators are also used for the testing of displays, MEMS technology, solenoids as well as for mass spectrometry and related scientific applications.