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SPICE Device Models: Diode Example–Part 2
2019.05.09
Points of this article
・There are two types of SPICE models: “device models” and “subcircuit models”.
・Characteristics can be adjusted by changing parameter values of device models.
・Device models are based on theoretical equations, and so simulation results are limited to the range that can be expressed by such equations (in some cases they may differ from actual behavior).
Following the previous article (Part 1), the explanation of SPICE device models was continued, using as an example a device model of a diode.
SPICE Device Models: Adjusting Parameters in Diode Device Model
In a device model, parameters are set, and so it is easy to see that if the settings in the model description are changed, these changes will be reflected in the simulation results. Below we present an example in which VF in the previously described diode device model has been adjusted.
In order to adjust the diode VF, IS (the saturation current) is changed. The equation for IF in Part 1 is IF = IS*exp(Vd/N*Vt)-1), and from the equation we see that a change in IS is proportional to a change in IF. The graph shows simulation results for the IF-VF characteristic when the IS value is made 10 times greater, and reduced to 1/10 the previous value. The IF for VF = 0.7 V is increased and decreased by a factor of 10.
In order to understand the relationships between parameters and diode characteristics, the model equations and parameters must be understood.
Limits to SPICE Device Models
Device models essentially represent the characteristics of theoretical equations of the model. Hence characteristics that cannot be expressed by theoretical equations are not reflected in simulation results. Simulation results must be interpreted keeping this limitation in mind.
The graphs below show IF-VF characteristics of diodes different from those discussed above. On the left are typical characteristics of an actual diode as given by the datasheet; on the right are simulation results for the device model for this diode.
It should be clear that, when comparing the linearity of IF-VF characteristics, simulation results are based on theoretical equations.
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Electrical Circuit Design
- Soldering Techniques and Solder Types
- Seven Tools for Soldering
- Seven Techniques for Printed Circuit Board Reworking
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Basic Alternating Current (AC)
- AC Circuits: Alternating Current, Waveforms, and Formulas
- Complex Numbers in AC Circuit
- Electrical Reactance
- What is Impedance? AC Circuit Analysis and Design
- Impedance Measurement: How to Choose Methods and Improve Accuracy
- Impedance Matching: Why It Matters for Power Transfer and Signal Reflections
- Resonant Circuits: Resonant Frequency and Q Factor
- RLC Circuit: Series and Parallel, Applied circuits
- What is AC Power? Active Power, Reactive Power, Apparent Power
- Power Factor: Calculation and Efficiency Improvement
- What is PFC?
- Boundary Current Mode (BCM) PFC: Examples of Efficiency Improvement Using Diodes
- Continuous Current Mode (CCM) PFC: Examples of Efficiency Improvement Using Diode
- LED Illumination Circuits：Example of Efficiency Improvement and Noise Reduction Using MOSFETs
- PFC Circuits for Air Conditioners：Example of Efficiency Improvement Using MOSFETs and Diodes
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Basic Direct Current (DC)
- Ohm’s Law: Voltage, Current, and Resistance
- Electric Current and Voltage in DC Circuits
- Kirchhoff’s Circuit Laws
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- Thevenin’s Theorem: DC Circuit Analysis
- Norton’s Theorem: Equivalent Circuit Analysis
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Thermal design
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About Thermal Design
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- A Mutual Understanding of Thermal Design
- Fundamentals of Thermal Resistance and Heat Dissipation: About Thermal Resistance
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- Fundamentals of Thermal Resistance and Heat Dissipation : Thermal Resistance in Emission
- Thermal Resistance Data: JEDEC Standards, Thermal Resistance Measurement Environments, and Circuit Boards
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- Thermal Resistance Data: θJA and ΨJT in Estimation of TJ: Part 1
- Thermal Resistance Data: θJA and ΨJT in Estimation of TJ: Part 2
- Surface Temperature Measurements: Methods for Fastening Thermocouples
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- Surface Temperature Measurements: Influence of the Thermocouple
- Estimating TJ: Basic Calculation Equations
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- Estimating TJ: Calculation Example Using Transient Thermal Resistance
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- Collection of Important Points Relating to Thermal Design
Switching Noise
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Dealing with Noise Using Capacitors
- Understanding the Frequency Characteristics of Capacitors, Relative to ESR and ESL
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Dealing with Noise Using Inductors
- Frequency-Impedance Characteristics of Inductors and Determination of Inductor’s Resonance Frequency
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Simulation
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Foundations of Electronic Circuit Simulation Introduction
- About SPICE
- SPICE Simulators and SPICE Models
- Types of SPICE simulation: DC Analysis, AC Analysis, Transient Analysis
- Types of SPICE simulation: Monte Carlo
- Convergence Properties and Stability of SPICE Simulations
- Types of SPICE Model
- SPICE Device Models: Diode Example–Part 1
- SPICE Device Models: Diode Example–Part 2
- SPICE Subcircuit Models: MOSFET Example―Part 1
- SPICE Subcircuit Models: MOSFET Example―Part 2
- SPICE Subcircuit Models: Models Using Mathematical Expressions
- About Thermal Models
- About Thermal Dynamic Model
- Summary
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- About Thermal Simulations of DC-DC Converters
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