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Examples<br />

Transient Noise Analysis Example 2—Switched Capacitor Filter<br />

Figure 21-50. AC & Noise Simulation of Amplifier Macromodel<br />

Switch Noise Model<br />

Instead of MOS transistors, a switch macromodel is used to perform the complete circuit<br />

simulations. To compute transient noise simulations, noise sources have been added to the<br />

switches. We have considered that a switch only generates thermal noise. A current source has<br />

been included between the source and the drain and its Power Spectral Density is a function of<br />

R ον , as follows:<br />

Simulation Results of the Complete Circuit<br />

Transient simulation results are shown below. In Figure 21-51 the first curve represents the<br />

impulse response of the circuit. The second curve represents the RMS value of noise generated<br />

at the output of the filter in the frequency band (1Hz, 50kHz). The RMS result is approximately<br />

8μV. This has been obtained by performing about 20 runs including noise sources. This curve<br />

1376<br />

Eldo® User's Manual, 15.3

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