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===AC Sensitivity Test===

The AC Sensitivity Test calculates the small-signal sensitivity of an output port to all device values and model [[parameters]] over a range of frequencies. The output port for sensitivity calculation is specified by a pair of positive and negative (reference) nodes. You can also prespecify whether the plots use decibels or magnitude, or degrees or radians.

===Distortion Test===

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===Small-Signal Transfer Function Test===

The Transfer Function Test calculates the small-signal transfer function of your circuit by linearizing it around its DC operating point. It generates the input impedance, output impedance and voltage gain seen across your circuit from the input port to the output port. All you need to do is specify the the input source and the output port.

For the simple voltage divider circuit of Tutorial Lesson 1 consisting of two resistors R1 = 1k and R2 = 2k, the transfer function is requested with the output port set between node 2 to ground (across R2), and the voltage source set as the input port. The test results for this example are shown in the opposite figure. The input impedance seen through the voltage source is R1 + R2 = 3k. The output impedance seen from the output port is the parallel combination R1 || R2 = 666.67. The transfer function is V2/V1 = 0.667.

===Pole-Zero Test===

The Pole-Zero Test generates a list of small-signal poles and zeros of the transfer function of your circuit given the input and output nodes.

Specify the input and output ports by the Positive and Negative (Reference) node numbers. To define the transfer function, you have two options: voltage gain by choosing "(output voltage)/(input voltage)" or trans-impedance by choosing "(output voltage)/(input current)". You can instruct the program to compute "Poles Only", or "Zeros Only", or "Pole & Zero".

The results of a Pole-Zero test is displayed as a table. As an example, consider the RLC circuit of Tutorial Lesson 2. Using the voltage gain definition for the transfer function, the Pole-Zero test reports two poles listed below:

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===Noise Test===

The Noise Test analyzes the device-generated noise over a range of frequencies. For this test you provide an input source, an output port and a range of frequencies. [[RF.Spice A/D]] calculates the noise contributions of each device (and each noise generator within each device) to the output port voltage. The program also calculates the equivalent to the output noise referred back to the specified input source. This is what is meant by the "Input Noise". The calculated value of the noise over the specified range of frequencies corresponds to the spectral density of the signal viewed as the square root of a stationary Gaussian stochastic process. After calculating the spectral densities, the simulator integrates these values over the frequency range to arrive at the total noise voltage/current over this frequency range. This calculated value corresponds to the variance of the circuit variable viewed as the square root of a stationary gaussian process.

As for the specific noise sources, they include the "shot" noise associated with the DC currents in semiconductor devices and the "thermal" noise associated with resistance. Semiconductors also display "flicker" (1/f) noise. However, due to the lack of a unified model, [[RF.Spice A/D]] handles this type of noise on a "case by case" basis. There are flicker noise parameters available for transistors in the list of model parameters. The program can also provide the noise gain associated with the 1/f source.

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