SimElectronics™

PJFET - Model SPICE-compatible P-Channel JFET

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SPICE-Compatible Semiconductors

Description

The PJFET block represents a SPICE-compatible P-channel JFET.

The PJFET block model includes the following components:

• Source-Gate Current-Voltage Model

• Drain-Gate Current-Voltage Model

• Source-Drain Current-Voltage Model

• Junction Charge Model

• Temperature Dependence

Source-Gate Current-Voltage Model

The block provides the following relationship between the source-gate current I_sg and the source-gate voltage V_sg after adjusting the applicable model parameters for temperature.

Where:

• IS is the Saturation current, IS parameter value.

• 

• ND is the Emission coefficient, ND parameter value.

• q is the elementary charge on an electron.

• k is the Boltzmann constant.

• T is the diode temperature:

  • If you select Device temperature for the Model temperature dependence using parameter, T is the sum of the Circuit temperature value plus the Offset local circuit temperature, TOFFSET parameter value. The Circuit temperature value comes from the SPICE Environment Parameters block, if one exists in the circuit. Otherwise, it comes from the default value for this block.

  • If you select Fixed temperature for the Model temperature dependence using parameter, T is the Fixed circuit temperature, TFIXED parameter value.

• GMIN is the diode minimum conductance. By default, GMIN matches the Minimum conductance GMIN parameter of the SPICE Environment Parameters block, whose default value is 1e-12. To change GMIN, add a SPICE Environment Parameters block to your model and set the Minimum conductance GMIN parameter to the desired value.

Drain-Gate Current-Voltage Model

The block provides the following relationship between the drain-gate current I_dg and the drain-gate voltage V_dg after adjusting the applicable model parameters for temperature.

Applicable Range of Vdg Values	Corresponding Idg Equation

Source-Drain Current-Voltage Model

The block provides the following relationship between the source-drain current I_sd and the source-drain voltage V_sd in normal mode (V_sd ≥ 0) after adjusting the applicable model parameters for temperature.

Applicable Range of Vsg and Vdg Values	Corresponding Isd Equation

Where:

• V_to is the Threshold voltage, VTO parameter value.

• β is the Transconductance, BETA parameter value.

• λ is the Channel modulation, LAMBDA parameter value.

The block provides the following relationship between the source-drain current I_sd and the source-drain voltage V_sd in inverse mode (V_sd < 0) after adjusting the applicable model parameters for temperature.

Applicable Range of Vsg and Vdg Values	Corresponding Isd Equation

Junction Charge Model

The block provides the following relationship between the source-gate charge Q_sg and the source-gate voltage V_sg after adjusting the applicable model parameters for temperature.

Applicable Range of Vsg Values	Corresponding Qsg Equation

Where:

• FC is the Capacitance coefficient FC parameter value.

• VJ is the Junction potential VJ parameter value.

• CGS is the Zero-bias GS capacitance, CGS parameter value.

• MG is the Grading coefficient, MG parameter value.

• 

• 

• 

The block provides the following relationship between the drain-gate charge Q_dg and the drain-gate voltage V_dg after adjusting the applicable model parameters for temperature.

Applicable Range of Vdg Values	Corresponding Qdg Equation

Where:

• CGD is the Zero-bias GD capacitance, CGD parameter value.

Temperature Dependence

Several transistor parameters depend on temperature. There are two ways to specify the transistor temperature:

• When you select Device temperature for the Model temperature dependence using parameter, the transistor temperature is

  

  where:

  • T_C is the Circuit temperature parameter value from the SPICE Environment Parameters block. If this block doesn't exist in the circuit, T_C is the default value of this parameter.

  • T_O is the Offset local circuit temperature, TOFFSET parameter value.

• When you select Fixed temperature for the Model temperature dependence using parameter, the transistor temperature is the Fixed circuit temperature, TFIXED parameter value.

The block provides the following relationship between the saturation current IS and the transistor temperature T:

where:

• IS is the Saturation current, IS parameter value.

• T_meas is the Parameter extraction temperature, TMEAS parameter value.

• XTI is the Saturation current temperature exponent, XTI parameter value.

• EG is the Energy gap, EG parameter value.

• 

• ND is the Emission coefficient, ND parameter value.

The block provides the following relationship between the junction potential VJ and the transistor temperature T:

where:

• VJ is the Junction potential VJ parameter value.

• 

• 

The block provides the following relationship between the gate-source junction capacitance CGS and the transistor temperature T:

where:

• CGS is the Zero-bias GS capacitance, CGS parameter value.

The block uses the CGS(T) equation to calculate the gate-drain junction capacitance by substituting CGD (the Zero-bias GD capacitance, CGD parameter value) for CGS.

The block provides the following relationship between the forward and reverse beta and the transistor temperature T:

where β is the Transconductance, BETA parameter value.

Basic Assumptions and Limitations

The model is based on the following assumptions:

• The PJFET block does not support noise analysis.

• The PJFET block applies initial conditions across junction capacitors and not across the block ports.

Dialog Box and Parameters

Main Tab

Device area, AREA

The transistor area. This value multiplies the Transconductance, BETA, Zero-bias GS capacitance, CGS, Zero-bias GD capacitance, CGD, and Saturation current, IS parameter values. It divides the Source resistance, RS and Drain resistance, RD parameter values. The default value is 1 m². The value must be greater than 0.

Number of parallel devices, SCALE

The number of parallel transistors the block represents. This value multiplies the output current and device charges. The default value is 1. The value must be greater than 0.

Threshold voltage, VTO

The gate-source voltage above which the transistor produces a nonzero drain current. The default value is -2 V.

Transconductance, BETA

The derivative of drain current with respect to gate voltage. The default value is 1e-04 A/m²/V². The value must be greater than or equal to 0.

Channel modulation, LAMBDA

The channel-length modulation. The default value is 0 1/V.

Saturation current, IS

The magnitude of the current that the ideal diode equation approaches asymptotically for very large reverse bias levels. The default value is 1e-14 A/m². The value must be greater than or equal to 0.

Emission coefficient, ND

The transistor emission coefficient or ideality factor. The default value is 1. The value must be greater than 0.

Source resistance, RS

The transistor source resistance. The default value is 0 m²*Ω. The value must be greater than or equal to 0.

Drain resistance, RD

The transistor drain resistance. The default value is 0 m²*Ω. The value must be greater than or equal to 0.

Junction Capacitance Tab

Model junction capacitance

Select one of the following options for modeling the junction capacitance:

• No — Do not include junction capacitance in the model. This is the default option.

• Yes — Specify zero-bias junction capacitance, junction potential, grading coefficient, forward-bias depletion capacitance coefficient, and transit time.

Zero-bias GS capacitance, CGS

The value of the capacitance placed between the gate and the source. This parameter is only visible when you select Yes for the Model junction capacitance parameter. The default value is 0 F/m². The value must be greater than or equal to 0.

Zero-bias GD capacitance, CGD

The value of the capacitance placed between the gate and the drain. This parameter is only visible when you select Yes for the Model junction capacitance parameter. The default value is 0 F/m². The value must be greater than or equal to 0.

Junction potential VJ

The junction potential. This parameter is only visible when you select Yes for the Model junction capacitance parameter. The default value is 1 V. The value must be greater than 0.01 V.

Grading coefficient, MG

The transistor grading coefficient. The default value is 0.5. The value must be greater than 0 and less than 0.9.

Capacitance coefficient FC

The fitting coefficient that quantifies the decrease of the depletion capacitance with applied voltage. This parameter is only visible when you select Yes for the Model junction capacitance parameter. The default value is 0.5. The value must be greater than or equal to 0 and less than or equal to 0.95.

Specify initial condition

Select one of the following options for specifying an initial condition:

• No — Do not specify an initial condition for the model. This is the default option.

• Yes — Specify the initial diode voltage.

  Note   The PJFET block applies the initial diode voltage across the junction capacitors and not across the ports.

Initial condition voltage ICVDS

Drain-source voltage at the start of the simulation. This parameter is only visible when you select Yes for the Model junction capacitance and Yes for the Specify initial condition parameter. The default value is 0 V.

Initial condition voltage ICVGS

Gate-source voltage at the start of the simulation. This parameter is only visible when you select Yes for the Model junction capacitance and Yes for the Specify initial condition parameter. The default value is 0 V.

Temperature Tab

Model temperature dependence using

Select one of the following options for modeling the diode temperature dependence:

• Device temperature — Use the device temperature, which is the Circuit temperature value plus the Offset local circuit temperature, TOFFSET value. The Circuit temperature value comes from the SPICE Environment Parameters block, if one exists in the circuit. Otherwise, it comes from the default value for this block.

• Fixed temperature — Use a temperature that is independent of the circuit temperature to model temperature dependence.

Saturation current temperature exponent, XTI

The order of the exponential increase in the saturation current as temperature increases. The default value is 0. The value must be greater than or equal to 0.

Activation energy, EG

The energy gap that affects the increase in the saturation current as temperature increases. The default value is 1.11 eV. The value must be greater than 0.1 eVi.

Offset local circuit temperature, TOFFSET

The amount by which the transistor temperature differs from the circuit temperature. This parameter is only visible when you select Device temperature for the Model temperature dependence using parameter. The default value is 0 K.

Fixed circuit temperature, TFIXED

The temperature at which to simulate the transistor. This parameter is only visible when you select Fixed temperature for the Model temperature dependence using parameter. The default value is 300.15 K. The value must be greater than 0.

Parameter extraction temperature, TMEAS

The temperature at which the transistor parameters were measured. The default value is 300.15 K. The value must be greater than 0.

Ports

The block has the following ports:

G

Electrical conserving port associated with the transistor gate terminal.

D

Electrical conserving port associated with the transistor drain terminal.

S

Electrical conserving port associated with the transistor source terminal.

References

[1] G. Massobrio and P. Antognetti. Semiconductor Device Modeling with SPICE. 2nd Edition, McGraw-Hill, 1993. Chapter 3.

See Also

NJFET, P-Channel JFET

Photodiode

PNP