Overview

We present here an example of an input file for the simulator Spice 2G and other equivalent Spice versions. A main purpose of this example is to illustrate the use of diodes for parasitic junctions and the use of scale factors. General information about Spice, and about the models in it, is provided elsewhere [ ^{[1] [2] [3] [4]}]. The reader is warned, however, that Spice model levels 1, 2, and 3, as well as many others, are in general inadequate for analog design (Secs. 3.12, 4.9, and 4.10 and App. B).

In Spice 2G, capacitance parameters for MOS transistor models are conveniently specified normalized to area or length. This practice, however, is not followed for models of bipolar transistors and diodes. For convenience, then, one can specify a fictitious unit diode (1- ?m by 1- ?m area) and a fictitious unit transistor (1- ?m emitter width) and then can use an appropriate scale factor to specify the device connections.

Our circuit example is shown in Fig. C.1. The devices are assumed laid out as in Fig. C.2, and they are made using the process of Examples 5.1 and 5.2. The Spice input file is as follows:

CIRCUIT EXAMPLE** Element Specification*_______________________*vdd 1 0 dc 2.5vss 0 2 dc 2.5m1 1 1 3 2 mn w=10u 1=3u as=30p ad=30p ps=26u pd=26um2 2 2 4 4 mp w=20u 1=3u as=60p ad=60p ps=46u pd=26u<a name="719"></a><a name="IDX-270"></a>q1 3 0 4 2 qn 12 dl 2 4 jd...