Recognizing Gate, Source & Drain for NMOS & PMOS

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In summary, the image shows an NMOS (M8) and PMOS (M7B) with arrows indicating the source terminal. However, in some cases, the source and drain may be reversed depending on the mode of operation.
  • #1
nobrainer612
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Homework Statement



I saw this image in the internet. I want to learn how to recognize the gate, source and drain for NMOS and PMOS.

24gknpd.jpg



The Attempt at a Solution



I don't know if I am correct or not.
M8 ( with an arrow coming out ) is NMOS. M7B (with an arrow going in) is a PMOS.
I know where the gate of a NMOS and PMOS. But I really have no idea how to recognize the source and drain for PMOS and NMOS.

I found that there are many version in the internet. Like in LTSpice, Source is always next to the gate. But I am not sure for the picture above.

Thank you
 
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  • #2
nobrainer612 said:

Homework Statement



I saw this image in the internet. I want to learn how to recognize the gate, source and drain for NMOS and PMOS.

24gknpd.jpg



The Attempt at a Solution



I don't know if I am correct or not.
M8 ( with an arrow coming out ) is NMOS. M7B (with an arrow going in) is a PMOS.
I know where the gate of a NMOS and PMOS. But I really have no idea how to recognize the source and drain for PMOS and NMOS.

I found that there are many version in the internet. Like in LTSpice, Source is always next to the gate. But I am not sure for the picture above.

Thank you

Basically, the arrow is the source.

This assumes the drain (D) is more + than the source (S) for an N channel, and vice-versa for a P channel.

HOWEVER: MOS devices can be run in the inverted mode. So for example an N channel might have the drain more - than the source. In which case the device behaves as though it's got the S and D terminals reversed. But still, the convention is to call the arrowed terminal the source.

(There is often a built-in diode between the S and D so that operation in the inverted mode is limited to saturation conditions. The inverted mode is very seldom used. I once ran across it at work & it turned out to be an inadvertent connection!)
 

1. What is the purpose of recognizing the gate, source, and drain in NMOS and PMOS transistors?

The gate, source, and drain are the three main regions of a MOSFET transistor. Recognizing these regions is crucial in understanding the behavior and functionality of the transistor. The gate controls the flow of current between the source and drain, while the source is the source of the current and the drain is where the current exits the transistor.

2. How can I identify the gate, source, and drain in a NMOS or PMOS transistor?

In both NMOS and PMOS transistors, the gate is the region that is insulated from the source and drain by a thin layer of oxide. This can be identified by its larger size compared to the source and drain regions. The source and drain are typically doped regions of the semiconductor material, and the drain is usually connected to a larger contact compared to the source.

3. What happens if the gate, source, or drain is incorrectly identified in a MOSFET transistor?

If the gate, source, or drain is incorrectly identified, it can lead to incorrect assumptions about the behavior of the transistor. This can result in errors in circuit design and can potentially damage the transistor. Therefore, it is important to correctly identify these regions to ensure proper functioning of the transistor.

4. Is there a difference in recognizing the gate, source, and drain in NMOS and PMOS transistors?

Yes, there is a difference in recognizing the gate, source, and drain in NMOS and PMOS transistors. In NMOS transistors, the source is connected to the ground and the drain is connected to the voltage supply, while in PMOS transistors, the source is connected to the voltage supply and the drain is connected to the ground. This difference is important to consider when designing circuits using these transistors.

5. Are there any tools or techniques that can aid in identifying the gate, source, and drain in a MOSFET transistor?

There are various tools and techniques that can aid in identifying the gate, source, and drain in a MOSFET transistor. One common method is to use a multimeter to measure the resistance between different regions of the transistor. The gate will typically have a high resistance compared to the source and drain. Additionally, many online resources and textbooks provide diagrams and illustrations that can help in identifying these regions.

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