AC Noise Test


This simulation analyzes device-generated noise over a range of frequencies. The user provides an input source and an output source and a range of frequencies. The simulator calculates the noise contributions of each device (and each noise generator within each device) to the output port voltage. The simulator also calculates the equivalent to the output noise referred back to the specified input source. This is what the program means by input noise. The calculated value of the noise over the range of frequencies corresponds to the spectral density of the circuit variable 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.

noise_circuit.gif (4604 bytes)

The tabular results to a noise analysis of the circuit above are shown below. First, the integrated noise results are shown. This represents the total input and output noises as a result of contributions from the discrete devices in the circuit. (namely, the resistor).
The results are the square root of what Berkeley Spice generates. This is because Berkeley spice gives values that are proportional to the noise power rather than the noise voltage.

Below, the spectral distribution of noise is given from 1K to 10K with 10 points per decade.