... | ... | @@ -19,3 +19,22 @@ Those 1.75 volts offset is called the "virtual" zero point. |
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Figure 1 shows the schematic of stage 4.
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image::https://es.technikum-wien.at/openlab/openlab_wiki/wikis/img/sig_proc_osci_hardware/sig_proc_osci_hardware_stage4.PNG[caption="Figure 1: ",title="Schematic of stage 4 of the OpenLab oscilloscope front-end",align="center"]
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Figure 2 shows the input and output of the fourth stage. To demonstrate the behavior of this front-end stage, a test signal was applied.
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This waveform is a sinusoidal signal with a frequency of 1kHz and a amplitude of 5V.
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image::https://es.technikum-wien.at/openlab/openlab_wiki/wikis/img/sig_proc_osci_hardware/sig_proc_osci_hardware_stage4_ltspice.PNG[caption="Figure 1: ",title="Relation between IN and OUT of stage 4. The test signal is a 5V 1kHz sine",align="center"]
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The input of stage 4, which is applied by stage 3, is represented by the red waveform. The output of stage 4 is shown in blue.
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As mentioned before, the third amplification stage was selected in order to correctly amplify the input signal.
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As shown in figure 2, the output of stage 4 is centered at 1.75V. This is the previously mentioned virtual zero point of the signal.
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It enables the measurement of negative signals with non-differential ADCs. |
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