# Differentiate Operator

The Differentiate operator calculates the discrete derivative of a waveform.

The most accurate derivative of your waveform is achieved in the real-time acquisition mode with the sin(x)/x interpolation filter enabled.

You can use Differentiate to measure the instantaneous slope of a waveform. For example, the slew rate of an operational amplifier may be measured using the Differentiate operator. The Differentiate algorithm is applied in two different ways depending on whether or not the Low Pass and Align Phase box is checked.

Low Pass and Align Phase Enabled

Imagine the following four sample points in your waveform.

When the Low Pass and Align Phase feature is enabled, the slope between points 3 and 1 is calculated and divided by two. This result is then plotted at point 2. Then the slope between points 2 and 4 is calculated, divided by two, and the result is plotted at point 3 (and so on). The algorithm is defined this way to preserve the phase relationship between the input and the function.

Low Pass and Align Phase NOT Enabled

Imagine the following four sample points in your waveform.

When the Low Pass and Align Phase feature is disabled, the slope between points 2 and 1 is calculated and the result is then plotted at point 1. Then the slope between points 2 and 3 is calculated and the result is plotted at point 2 (and so on).

## Display Setup

Each operator's setup includes a Setup section that has the selections that are shown in the following generic setup dialog box. Use these settings to control the display of the operator's output waveform, including turning the display on or off. Use the Name field to display an identifying name to the waveform which can be helpful for screen captures or when multiple waveforms are displayed. The settings also include the output waveform's color, scaling, and signal type. The scaling Automatic selection allows the output waveform to track changes to the scaling of the input waveform. This is the setting that you would normally want to use.

The signal Pattern can be used for BER (Bit Error Ratio), SNDR (Signal to Noise and Distortion Ratio), and other measurements. You can specify the math function has the same pattern as the input waveform (Track Input), Auto Detect the pattern, choose a Known Pattern from a list, or specify your own pattern using a Pattern File.