Let%27s delve into the details of the drain-source voltage swing in a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).
1. Understanding On-State Resistance (RDS(on)):
- One of the most prominent specifications on MOSFET datasheets is the drain-to-source on-state resistance, abbreviated as RDS(on).
- The simplified model assumes that when the FET is in cutoff, the resistance between the source and drain is extremelyLet%27s delve into the details of the drain-source voltage swing in a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).
1. Understanding On-State Resistance (RDS(on)):
- One of the most prominent specifications on MOSFET datasheets is the drain-to-source on-state resistance, abbreviated as RDS(on).
- The simplified model assumes that when the FET is in cutoff, the resistance between the source and drain is extremely high, effectively zero current flow.
- When the FET%27s gate-to-source voltage (VGS) exceeds the threshold voltage (VTH), it enters the "on state," and the drain and source are connected by a channel with resistance equal to RDS(on).
- However, this model doesn%27t fully align with the actual electrical behavior of a MOSFET.
2. Triode Region and RDS(on):
- The FET does not have a simple "on state." Instead, it can be in the triode region or the saturation region (ignoring subthreshold conduction).
- For switch circuits (e.g., driving a motor or controlling a relay), we consider the triode region.
- In the triode region, the relationship between drain-to-source current (ID) and drain-to-source voltage (VDS) is linear (resistive).
- However, the "resistance" is not constant like a simple resistor; it depends on the gate-to-source voltage:
- RDS(on) = 1 / (μnCoxW/L) * (VGS - VTH)
3. Gate-to-Source Voltage Influence:
- RDS(on) is influenced by the gate-to-source voltage.
- Example: Consider Fairchild%27s NDS351AN MOSFET with a typical threshold voltage of 2.1 V.
- Driving this FET with a 3.3 V logic signal won%27t achieve the advertised on-state resistance performance because RDS(on) corresponds to a specific gate-to-source voltage, not just VTH.
In summary, understanding RDS(on) and its dependence on gate-to-source voltage is crucial for designing efficient MOSFET-based circuits. These parameters impact switching behavior and overall system performance ¹².
(1) Understanding MOSFET On-State Drain-to-Source Resistance. https://www.allaboutcircuits.com/technical-articles/understanding-mosfet-on-state-drain-to-source-resistance/.
(2) MOSFET Amplifier: Maximum Signal Swing without Clipping. https://electronics.stackexchange.com/questions/304026/mosfet-amplifier-maximum-signal-swing-without-clipping.
(3) What happens to a MOSFET as the drain-source voltage increases?. https://siliconvlsi.com/what-happens-to-a-mosfet-as-the-drain-source-voltage-increases/.
(4) Calculating Drain voltage of a mosfet - Electrical Engineering Stack .... https://electronics.stackexchange.com/questions/468333/calculating-drain-voltage-of-a-mosfet. high, effectively zero current flow.
- When the FET%27s gate-to-source voltage (VGS) exceeds the threshold voltage (VTH), it enters the "on state," and the drain and source are connected by a channel with resistance equal to RDS(on).
- However, this model doesn%27t fully align with the actual electrical behavior of a MOSFET.
2. Triode Region and RDS(on):
- The FET does not have a simple "on state." Instead, it can be in the triode region or the saturation region (ignoring subthreshold conduction).
- For switch circuits (e.g., driving a motor or controlling a relay), we consider the triode region.
- In the triode region, the relationship between drain-to-source current (ID) and drain-to-source voltage (VDS) is linear (resistive).
- However, the "resistance" is not constant like a simple resistor; it depends on the gate-to-source voltage:
- RDS(on) = 1 / (μnCoxW/L) * (VGS - VTH)
3. Gate-to-Source Voltage Influence:
- RDS(on) is influenced by the gate-to-source voltage.
- Example: Consider Fairchild%27s NDS351AN MOSFET with a typical threshold voltage of 2.1 V.
- Driving this FET with a 3.3 V logic signal won%27t achieve the advertised on-state resistance performance because RDS(on) corresponds to a specific gate-to-source voltage, not just VTH.
In summary, understanding RDS(on) and its dependence on gate-to-source voltage is crucial for designing efficient MOSFET-based circuits. These parameters impact switching behavior and overall system performance ¹².
(1) Understanding MOSFET On-State Drain-to-Source Resistance. https://www.allaboutcircuits.com/technical-articles/understanding-mosfet-on-state-drain-to-source-resistance/.
(2) MOSFET Amplifier: Maximum Signal Swing without Clipping. https://electronics.stackexchange.com/questions/304026/mosfet-amplifier-maximum-signal-swing-without-clipping.
(3) What happens to a MOSFET as the drain-source voltage increases?. https://siliconvlsi.com/what-happens-to-a-mosfet-as-the-drain-source-voltage-increases/.
(4) Calculating Drain voltage of a mosfet - Electrical Engineering Stack .... https://electronics.stackexchange.com/questions/468333/calculating-drain-voltage-of-a-mosfet.
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