Overview

Overview. The noise analysis previously performed has been restricted to hand calculation. The resulting advantages are insight into circuit operation, understanding the effects of various noise sources, and how the circuit elements affect the noise parameters. The price to be paid is that calculations are time-consuming and the resulting expressions are often cumbersome. The situation worsens when we are dealing with complex impedances, and when the noise analysis must be carried out at several frequencies.

Therefore, it seems reasonable to use existing electrical simulators, in order to perform fast and accurate noise analysis. However, attention must be paid to the following point: while almost all electrical simulators like SPICE have behind them a history of several decades during which they have been intensely tested and continuously improved, noise simulation is in a quite different position.

In practice, noise analysis is either available as an option in electrical simulators, or it may be performed with the few existing dedicated software packages.

In the former case, the circuit may have any topology and is described using the node-branch concept; a typical example is SPICE or any other member of the family (PSPICE, HSPICE, ISPICE, etc.). As made obvious in Chap. 7, the noise models employed are not necessarily the most efficient ones and up- dating them is a real necessity. Another limitation is the impossibility of directly accessing the four noise...