Voltage)/(input voltage) and the other of the form (output voltage)/(inputĬurrent). Two types of transfer functions are allowed: one of the form (output This circuit is then used to find the poles and zeros of the transfer function. Linearized, small-signal models for all the nonlinear devices in the circuit. Program first computes the DC operating point and then determines the PZ)Ĭomputes the poles and/or zeros in the small-signal AC transfer function. The pole-zero analysis portion of Spice (see. Not time dependent (for example, power supplies) are set to their DC value. Initial conditions are automatically determined by a DC analysis. Transient output variables as a function of time over a user-specified time interval. The transient analysis portion of Spice (see. Of the output variable with respect to the input. Unity and zero phase, so that output variables have the same value as the transfer function If the circuit has only one AC input, it is convenient to set that input to The desired output ofĪn AC small-signal analysis is usually a transfer function (voltage gain, transimpedance,Įtc.). The resultant linearĬircuit is then analyzed over a user-specified range of frequencies. Small-signal models for all of the nonlinear devices in the circuit. (see §1.1.1) of the circuit and determines linearized, The program first computes the DC operating point Output variables as a function of frequency. The AC small-signal portion of Spice (see. Over a user-specified range and the DC output variables are stored for each sequential source DC): a specified independent voltage or current source is stepped The DC analysis can also be used to generate DC transfer curves (see Input source, input resistance, and output resistance can also be computed during DC solution. TF), which is the ratio of output variable to If required, the DC small-signal value of a transferįunction (see. Small-signal models for nonlinear devices. TRAN) to determine the transient initial conditions, and prior toĪC small-signal analyses (see. OP) of the circuit with inductors shorted and capacitors opened.Ī DC analysis is automatically performed prior to a transient analysis (see The DC analysis portion of Spice determines the quiescent operating point (see MOS2, MOS3, and MOS4 include second-order effects such as channel-length modulation, subthreshold conduction, scattering-limited velocity saturation, small-size effects, and charge-controlled capacitances. Six MOSFET models are implemented: MOS1 is described by a square-law I-V characteristic, MOS2 is an analytical model, while MOS3 is a semi-empirical model MOS6 is a simple analytic model accurate in the short-channel region MOS4 and MOS5 are the BSIM (Berkeley Short-channel IGFET Model) and BSIM2. The JFET model is based on the FET model of Shichman and Hodges. The diode model can be used for either junction diodes or Schottky barrier diodes. In either case, charge-storage effects, ohmic resistances, and a current-dependent output conductance may be included. The model for the BJT is based on the integral-charge model of Gummel and Poon however, if the Gummel-Poon parameters are not specified, the model reduces to the simpler Ebers-Moll model. Spice has built-in models for the semiconductor devices, and the user need specify only the pertinent model parameter values. While Spice 3 was developed to include new features, it continues to support thoseĬapabilities and models which remain in extensive use in the Spice 2 program. The Spice 3 version is based directly on Spice 2g6. Circuits may contain resistors, capacitors, inductors, mutual inductors, independent voltage and current sources, four types of dependent sources, lossless and lossy transmission lines (two separate implementations), switches, uniform distributed RC lines, and the five most common semiconductor devices: diodes, BJTs, JFETs, MESFETs, and MOSFETs. Spice is a general-purpose circuit simulation program for nonlinear DC, nonlinear transient, and linear AC analyses. Original description of Spice 3f4 have also been made throughout the text. This paragraph, is indicated with its own display style. In this edition material that is specific to MacSpice, such as This User's Guide closely follows the original
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