Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [source-follower]

A source follower (also known as a common drain amplifier) is one of three basic single-stage field effect transistor (FET) amplifier topologies, typically used as a voltage buffer. Use this tag along with the tag for the type of FET (e.g. "mosfet").

A source follower (also known as a common drain amplifier) is one of three basic single-stage field effect transistor (FET) amplifier topologies, typically used as a voltage buffer. Use this tag along with the tag for the type of FET (e.g. ).

23 questions
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How does adding a current source and extra resistor to source follower improve its performance?

This question is similar to FET - Source follower utilizing current source to lower voltage offset, although I do not entirely understand the explanations, which is why I am posting my own question. As part of an electronics lab, I was asked to…
corgiworld
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Reducing the offset voltage of a source follower

I am currently trying to reduce the offset voltage of the circuit attached below to less than +/- 2mV over a 1V to 4V input range. I have a few constraints for this task: I can use nmos, pmos and pmos4 but can't use nmos4 as the fabrication process…
Oreoluwa Adesina
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Source-Follower Large Signal Analysis as Level Shifter

I have a question about the MOS source-follower / common-drain stage. In particular, it's behaviour as a level shifter: The book mentions the following: I'm having some trouble figuring out how the drain current may increase by a factor of 2? The…
AlfroJang80
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Need help for pointing out, source follower circuit with current source, designing NMOS

I'm not sure did I solve this problem right. I made \$ r_{o2} \$ , which is resistance looking at Q2 drain. So I can get $$ g_{m,Q3} = 1.8m(A/V) $$ from $$A_v = \frac{r_{o2} || r_{o3}}{1/g_m + (r_{o2} || r_{o3})}$$ and I could get W/L by $$…
Pare Kanes
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Source follower basic question

I just want to clear my understanding about a basic source follower circuit. Following is the circuit Here is my question: Considering Vi > Vgs(th); Vo = Vi - Vgs. Also Vo = Id*Rs as shown in the picture. Now Id is defined by Vgs*gm. That much…
RAN
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Strange output with a LM7171 opamp (non-inverser amplifier)

I have a continuous input signal with a very high impedance and I need an output signal with a low impedance of 50Ω. That's why I've considered the LM7171 (High Output Current: 100 mA). I've tried to make the following non-inverser amplifier using a…
Luc
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Source Follower Output Biasing

I am trying to understand the Source Follower amplifier as a primitive buffer, and am running some simulations with a SPICE simulator. I have the amplifier hooked up as shown below with a current source acting as the bias for the NMOS transistor…
Dr. Watson
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Source Resistor of JFET Source-Follower

I am designing a simple Buffer to get the voltage of a high-impedanze source to an ADC (60k Impedance). For that I choosed an JFET in the source-follower configuration. simulate this circuit – Schematic created using CircuitLab To bias the gate to…
Feuerlink
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Tuning a potential sensor using a source-follower MOSFET

I am interested in building a simple but sensitive setup that would allow me to detect small potential changes (adsorption of ions) on the surface of the gate of a MOSFET - what is commonly referred to as an extended gate FET. As a reference, see…
Mowgli
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How can I improve this source follower circuit?

Previously I asked for help with a power supply for titanium anodizing and my requirements were too vague. After doing some testing I believe I have found a schematic which I was able to use and change for my requirements. I would like to improve…
Infernoman
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What does source follower mode mean?

I've been trying to build a CMOS-level XOR gate. I've been told my implementation won't work because some of the transistors are in "source follower mode". I've tried looking this up, but I can't find a simple description of the term. In simple…
Connor
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Source follower input/output swing

I found in this book at the page 271 a definition of the source follower input/output swing ( that i didn`t know as: $$ V_{in-pp} = V_{dd} - ( Vt + 2.V_{ds-sat} )$$ I tried to understand how to calculate this paramater (I've tried to consider the…
Mxm89
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What happens if the gate voltage exceeds the drain voltage in a source follower with an active load?

What happens if the gate voltage exceeds the drain voltage in a source follower with an active load? Here is the circuit: If we try to increase input voltage even more than Vdd, what happens then? The current source is constant. We may guess that…
mohammad rezza
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Separating power ground from control ground to exceed NMOS threshold voltage

I'm a novice circuit designer looking to create a high voltage source follower NMOS circuit. I originally planned to use a Teensy digital I/O pin as the gate control signal, so when the Teensy outputted high (3.3V) the source follower output voltage…
asyndeton256
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MOSFET analog output buffer for 0 V to 2.4 V signal

I have a signal that starts at 0 V and linearly increases to 2.4 V as output and I would like to buffer it such that it cannot be influenced by resistive loads. The issue is that the only buffer circuit I've learned is the source follower (common…
Saens
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