gnt mashup

At a glance

This tool integrates R. D. Middlebrook's theorems, collectively referred to as the General Network Theorem (GNT) as a new small-signal analysis gnt for Spectre/APS in Cadence Virtuoso's ADE L and ADE XL. These theorems allow to decompose a transfer function into lower-level transfer functions by use of signal injections. The interpretation of the lower-level transfer functions depends on the injection configuration. The GNT morphs into:

  • General Feedback Theorem (2GFT): decompose a transfer function in an ideal transfer function, loop gain, null loop gain and direct forward transmission.
  • Extra Element Theorem (NEET): find out the impact of one or more elements in the circuit on a transfer function.
  • Chain Theorem (2CT): find out loading effects between parts of a circuit, e.g. between amplifier stages.

Furthermore, arbitrary nesting of analyses is possible. You can now, for example,

  • analyze multiple-loop feedback circuits: calculate the total Mason's loop gain by nesting 2GFT analyses (this can be regarded as a multiple-loop extension of stb)
  • apply the NEET to find out the effect of multiple elements on circuit performance at once
  • find out the effect of interstage loading on loop gain, direct forward transmission from input to output, ... by nesting a 2CT in a 2GFT
  • find out the impact of a device on loop gain and stability by nesting a NEET in a 2GFT
  • ...

In addition, multiple transfer functions, e.g. input to output, power supply to output, input and output impedances, common-mode and differential mode... can be decomposed in one pass as MIMO systems are allowed.

Deep integration

The gnt analysis follows the same use model as other analyses such as ac, stb,... Results are included in the psf data and accessible in the usual ways (Results Browser and SKILL API). ADE L is fully supported, including parametric sweeps. ADE (G)XL modes such as corners, parameters, monte carlo sampling, sensitivity analysis, optimization, worst-case corners are supported.

Getting started guide

A walk-through document is included to get you started.

Example library

A library with examples and references to key publications is included.

More information

Downloads, documentation and references can be found on

An overview of an earlier version of the tool was presented at CDNLive EMEA 2014 (accompanying paper).