MOSFET input Voltage for saturation region

In summary, to enter the saturation region of a MOSFET, the following conditions must be met: VDS > VGS - VT, where VGS = VIN - VS- and VDS = Vs+ - Vs-. By plugging in the given parameters of VS+ = 1.0 V, VS- = -1.0 V, and VT = 0.5 V, we can determine that VIN must be between -0.5 V and 1.5 V. In this case, a VIN of -0.5 V would satisfy the condition and put the MOSFET in saturation.
  • #1
Piyush Gupta
2
0
I'm trying to solve for the minimum vIN such that MOSFET is in the saturation region. Here are the given parameters
VS+ = 1.0 V
VS- = - 1.0 V
VT = 0.5 V

In order to enter saturation I know that VDS > VGS - VT

VGS = VIN - VS-

VDS = Vs+ - Vs-, which is 2 V

Which means
2V > VIN - VS- - VT
2V > VIN - (- 1.0 V) - 0.5 V
2V > VIN + 0.5 V

I get a VIN of 1.5 Volts. The correct answer is -0.5 V. I'm just starting to learn electrical engineering and it would be great if someone can point out what's missing.
 

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  • #2
I figured it out.
VGS > VT
hence
VIN - VS- > 0.5 V
VIN + 1 > 0.5 V
VIN = -0.5
VIN can vary from -0.5 to 1.5;
 

1. What is the definition of saturation region in a MOSFET?

The saturation region in a MOSFET is a state where the device is fully turned on and the drain current is at its maximum value. In this region, the voltage between the gate and source (VGS) is high enough to create a conducting channel between the source and drain, allowing a large amount of current to flow through the device.

2. How does the input voltage affect the saturation region of a MOSFET?

The input voltage, specifically the gate-to-source voltage (VGS), is the key factor in determining the saturation region of a MOSFET. As the VGS increases, the device moves from the cutoff region, where it is non-conducting, to the saturation region, where it is fully conducting. In the saturation region, the drain current is directly proportional to VGS.

3. What is the typical range of VGS for the saturation region in a MOSFET?

The typical range of VGS for the saturation region in a MOSFET is between 2 and 5 volts. This range may vary depending on the specific characteristics and design of the device, but it is generally within this range.

4. What happens if the input voltage exceeds the saturation region in a MOSFET?

If the input voltage, specifically VGS, exceeds the saturation region in a MOSFET, the device will enter the triode region. In this region, the drain current becomes less dependent on VGS and more dependent on the drain-to-source voltage (VDS). The device will also experience a decrease in gain and an increase in output impedance.

5. How does the input voltage affect the switching speed of a MOSFET?

The input voltage, specifically VGS, plays a crucial role in the switching speed of a MOSFET. As the VGS increases, the device can be turned on faster, resulting in a faster switching speed. However, if the input voltage is too high, the device may enter the triode region, slowing down the switching speed. Therefore, it is important to carefully choose the input voltage to ensure optimal switching performance.

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