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Modeling Transistor Amplifier Self-Heating - Thermal Network

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

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Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Wed, 09/17/2025 - 20:36

Designer263565

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Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

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Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Wed, 09/17/2025 - 08:04

Designer247997

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Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

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Modeling Transistor Amplifier Self-Heating - Thermal Network JSAE 2025

Designer241497

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Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

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Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Mon, 03/10/2025 - 12:35

Designer261842

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Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Fri, 01/17/2025 - 21:34

Designer260001

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Welcome to the community!!

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Wed, 01/15/2025 - 16:03

Designer260730

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Welcome to the community!!

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Fri, 01/10/2025 - 13:28

Designer260641

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Welcome to the community!!

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Thu, 08/08/2024 - 11:54

Designer257738

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Welcome to the community!!

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

Copy of Modeling Transistor Amplifier Self-Heating - Thermal Network - on Mon, 07/22/2024 - 11:06

Designer257481

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Welcome to the community!!

Description

This example shows the importance of modeling thermal interaction effects, or "thermal crosstalk", in power dissipating circuits. The "design" is a simple transistor amplifier, using just an 8 Ohm pull-up resistor and an active pull-down NPN BJT. Both of these models are from our "Thermal and Electro-thermal" Components Library, so they have a thermal port that can connect to an external thermal network. These models output all power dissipated in the device as a thermal heat-flow into that network.

The thermal network includes the heat-sink's heat capacitance (0.1 J/degC) and heat transfer resistance to the ambient (10 degC/Watt). This assumes the resistor and transistor contribute heat to the same heat-sink. The transistor's thermal heat-flow path also includes an 8.8 degC/Watt resistance, to represent the Junction-to-Lead Thermal Resistance as published in the device datasheet (Diodes Inc. FZT869).

From the simulation results it is clear that the heat-sink temperature rises to nearly 120 degC (purple waveform), causing the transistor's junction temperature to approach 150 degC (average, red waveform). This is significantly higher than the value predicted in the companion design example: "Modeling Transistor Amplifier Self-Heating - Hot Part Monitor", which assumed the two devices were thermally isolated.

About text formats

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