- #1
nobrainer612
- 26
- 0
AC coupling using NMOS
Hello. What does AC coupling by using NMOS and PMOS actually means?
Hello. What does AC coupling by using NMOS and PMOS actually means?
Last edited:
In summary, the conversation is discussing the use of NMOS and PMOS for AC coupling. The NMOS circuit has been successfully built and produces a 200mV p-p output, but the PMOS circuit is not producing the same waveform or value. Further explanation is needed to understand the discrepancy.
- #2
yungman
- 5,718
- 241
The drain of M2 is AC coupled by C2 to drive the load R4.
The way the circuit work is M1 have the gate and drain shorted to set up the current which mirror to M2. The drain of M2 has positive voltage. So AC coupling is needed to bring it to ground reference level.
- #3
nobrainer612
- 26
- 0
Homework Statement
The problem is to perform AC coupling by using NMOS and PMOS
Homework Equations
The Attempt at a Solution
AC coupling by using NMOS is solved. Then I tried to build one by using PMOS, but the result from these 2 are different.
This is the NMOS circuit:
This is the result waveform from this circuit:
This is the PMOS circuit:
This is the result waveform from this circuit:
- #4
NascentOxygen
Staff Emeritus
Science Advisor
- 9,242
- 1,074
Perhaps you'd better explain what you don't like about the second circuit. It seems to me that in both you achieved an output of 200mV p-p, so I don't see anything amiss.
(I won't be able to help you further, but if you explain this, someone may be able to.)
(I won't be able to help you further, but if you explain this, someone may be able to.)
- #5
nobrainer612
- 26
- 0
my question is, shouldn't the blue wave from the circuit built by PMOS has the same waveform and value as NMOS?
- #6
NascentOxygen
Staff Emeritus
Science Advisor
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Oh! The invisible blue waveform. I had not noticed it!nobrainer612 said:
I now understand your concern.
1. What is AC coupling using NMOS and PMOS?
AC coupling using NMOS and PMOS is a technique used to remove the DC offset from an input signal while preserving the AC component. It involves using a capacitor and two complementary metal-oxide-semiconductor (CMOS) transistors, one NMOS and one PMOS, to block the DC component and pass the AC component of the input signal.
2. How does AC coupling using NMOS and PMOS work?
The input signal is first connected to the gate of the NMOS transistor, while the source is connected to ground. The drain of the NMOS is connected to the gate of the PMOS, and the source is connected to the power supply rail. A capacitor is connected between the drain of the PMOS and the output. The DC component of the input signal is blocked by the NMOS, while the AC component passes through to the PMOS. The PMOS then amplifies and inverts the signal, which is then passed through the capacitor to the output. This results in a purely AC output signal.
3. What are the advantages of using NMOS and PMOS in AC coupling?
One advantage is that CMOS technology offers low power consumption and high integration density, making it suitable for use in many applications. Additionally, the use of complementary transistors ensures that the output signal is not distorted and maintains a high signal-to-noise ratio. AC coupling using NMOS and PMOS also allows for the removal of large DC offsets, which may be present in some input signals.
4. What are the limitations of AC coupling using NMOS and PMOS?
One limitation is that the capacitor used in the circuit must be large enough to pass the desired AC frequency range without significant attenuation. This can result in a larger physical size of the circuit and may also introduce unwanted phase shifts. Additionally, the use of complementary transistors in the circuit requires precise matching, which can be challenging to achieve in practice.
5. What are some applications of AC coupling using NMOS and PMOS?
AC coupling using NMOS and PMOS is commonly used in audio amplifiers, where it allows for the removal of DC offsets and improves the overall sound quality. It is also used in data transmission systems, such as in high-speed serial communication, to remove DC offsets and restore the original signal. This technique can also be found in medical devices, instrumentation, and other electronic systems where a clean AC signal is required.
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