Another NMOS-transistor problem

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In summary, the conversation discusses a problem involving two NMOS transistors in series with various resistors. The goal is to find the voltage and current at different points in the circuit. The conversation includes a link to a diagram and the attempts at solving the problem, including the correct answer. In the end, the individual thanks the conversation partner for their help in solving the problem.
  • #1
Molecular
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[SOLVED] Another NMOS-transistor problem

I'm sorry for asking again so soon, but these transistors really give my head a spin.

Homework Statement


The problem is pretty much summed up by the following photograph:
http://img444.imageshack.us/img444/2338/transistorerul0.jpg

The Attempt at a Solution


To be quite honest I'm really stumped here. I can go over what I know (Or at least what I think I know):

Since everything displayed here is in series, I'm presuming the current over each element is the same. The voltage over R1 should be 10 - v1, basically meaning if I could find v1 I should be able to find the current R1 and thus the current in every other element connected aswell, which would make the problem easy.

Vgs for the first transistor is 5 volts, and vgs=vds for the second transistor. R1 and R2 should have the same voltage drop across them.
All in all, 15 volts dissipate over this circuits as vdd = 10 volts and vss = -5.

After this, it completely stops. I've got the correct answer, which is
v1 = 6 v
and
v2 = 2 v

So by my logic, the current over the first resistance is (10-6)/1000 = 4 mA.
This is where I get confused, because if v2 = 2v, doesn't that mean the voltage drop across the first transistor is 4v aswell?
But if it is, this indicates that 16 mA runs through it, which isn't really possible if only 4 mA runs through the first resistance.
I tried checking what the voltage vds over the first transistor had to have been in order to allow for 4mA to pass through, and as far as I can remember the answer I got was sqrt(2)+1. Which is a fairly ugly number so I'm presuming this is wrong.

Anyone got a hint that can push me in the correct direction? It would be greatly appreciated. I'm dying to understand these blasted transistors.
 
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  • #2
"Vgs for the first transistor is 5 volts..." Vgg=5 volts. Wouldn't Vgs=Vgg-V2?
 
  • #3
Aha, I see now, of course. Thanks!
I managed to solve it now by using four different equations, was quite a hustle but I've never figured it out if not for this!

Thanks again!
 

1. What is an NMOS transistor?

An NMOS (N-channel Metal-Oxide-Semiconductor) transistor is a type of field-effect transistor (FET) that uses a negatively charged channel of electrons to conduct current. It is commonly used in digital and analog circuits in electronic devices.

2. How does an NMOS transistor work?

An NMOS transistor consists of three terminals: source, drain, and gate. When a voltage is applied to the gate, it creates an electric field that controls the flow of electrons between the source and drain. When the gate voltage is high, the transistor is in the "on" state and allows current to flow. When the gate voltage is low, the transistor is in the "off" state and does not allow current to flow.

3. What are some applications of NMOS transistors?

NMOS transistors are commonly used in digital logic circuits, such as in microprocessors, memory chips, and other integrated circuits. They are also used in analog circuits, such as amplifiers and switches.

4. What are the advantages of using NMOS transistors?

NMOS transistors have a simple structure, low cost, and can be easily integrated into electronic devices. They also have a fast switching speed, making them suitable for high-speed applications. Additionally, they have a low power consumption, making them energy-efficient.

5. What are the limitations of NMOS transistors?

One limitation of NMOS transistors is that they can only operate with positive supply voltages, which can limit their use in certain applications. They also have a higher leakage current compared to other types of transistors, which can affect their performance. Additionally, they are more susceptible to damage from electrostatic discharge (ESD) and have a lower noise margin compared to complementary MOS (CMOS) transistors.

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