3.2 Overview of the Minimos-NT Small-Signal Capabilities

As depicted in the overview in Figure 3.5, the small-signal capabilities which were implemented into MINIMOS-NT can be divided into two branches:

1. Standard small-signal capabilities: general complex-valued amplitudes can be applied to an arbitrary number of terminals of the device. In combination with the frequency setting, the simulator can be used to calculate the respective complex-valued terminal currents or voltages. For example, this feature can be efficiently applied to extract the cut-off frequency $f_\textrm {T}$ of the simulated device.
2. Extended small-signal capabilities: for several simulation tasks such as the S-parameter extraction, it is necessary to calculate the complete admittance matrix of the device, which can be obtained by applying the unity voltage once to each terminal. Since the device is linearized, it does not matter which voltage is applied at the terminal (besides of numerical considerations). For the special case of the unity voltage, there is no subsequent division necessary to obtain the admittance value. By using the standard capabilities, the calculation of the matrix can be a cumbersome task, because appropriate stepping variables have to be defined and the respective post-processing for collecting these values has to be implemented and configured. Furthermore, speed-up features suitable for this kind of simulation task cannot be employed. See for example the discussion of the multiple right-hand-side feature in Section 4.3. For that reason, a feature for automatically calculating the complete admittance matrix is provided. Based on these features, various sets of intrinsic and extrinsic parameters can be extracted.

Figure 3.5: Overview of the MINIMOS-NT small-signal capabilities.

The main simulator output of the extended branch is the intrinsic (de-embedded) admittance matrix. Based on this matrix, the intrinsic capacitance and intrinsic scattering matrix can be calculated. As an optional feature these parameters can be transformed into extrinsic parameters in order to take parasitics introduced by the measurement set-up into account.

Both branches finally provide comfortable features to extract the cut-off frequency $f_\textrm {T}$ or additional figures of merit such as the maximum oscillation frequency $f_\mathrm{max}$. In addition, the user is able to inquire all small-signal simulation results (see Appendix A.6) and can employ the input-deck built-in functions to perform further calculations, which can then be written to the simulator output file. Thus, as a matter of improved usability no subsequent post-processing is necessary for the most common simulation tasks.

As already seen in Figure 3.5, all small-signal capabilities are available also for mixed-mode simulations, which are discussed in the second part of this chapter.