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Questions tagged [common-drain]

A common drain amplifier (also known as a source follower) 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").

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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 ...
Connor's user avatar
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Gain of 0 dB for a common drain using JFET

I need to design a circuit that has a gain of 0 dB that allows a voltage attack on a 100 Ω load. My first thought was to make a common-drain circuit since I had to use only JFETs. First I only used 1 ...
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Should I connect the Vout coupling capacitor of a common drain amplifier next to RD or RS?

When designing a common drain amplifier of the circuit linked below, I need to attach a coupling capacitor to the Vout of the circuit. I think a capacitor connected to Vout should be just below RD, is ...
Thne's user avatar
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Common Source vs. Common Drain for N-Channel Switches

Most discrete load switches I have seen (Using N-Channel FETs) have been in the common-source configuration. What, if any, are the operational differences between this and the common-drain ...
Tim Vermilyea's user avatar
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Common drain small signal analysis and unresolved question for FET

There is an amplifier circuit obtained between JFET and MOSFET. For the FET used in the circuit, \$I_{\text{DSS}} = 8\text{ mA}\$, \$V_{\text{GSoff}} = -3\text{ V}\$ and working point current is 1.42 ...
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How to get the gain for this MOSFET amplifier?

This is a common drain MOSFET amplifier: simulate this circuit – Schematic created using CircuitLab This is its small signal model at low frequency: simulate this circuit I am at a loss as to ...
joe doe's user avatar
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DC analysis of common-drain NMOS amplifier

The DC analysis is regarding the amplifier calculations, but that is not relevant to the topic. The equivalent DC circuit of the amplifier is: The known values are: \$R_{g1}=300\text{ k}\Omega\$, \$...
A6EE's user avatar
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Common drain JFET output resistance "problem"

The output resistance of small signal model for common drain JFET amplifier equals $$ \frac{1}{g_\text{m}} || R_{\text{ds(on)}} \parallel R_\text{S} $$ and since $$ R_{\text{ds(on)}} =\frac{1}{g_\text{...
lucenzo97's user avatar
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2 votes
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Op-amps vs common drain amplifier for photodiode integration

I've been playing around with photodiodes and op-amps lately, and thought it might be fun to construct a really crude camera with a dozen pixels. I was going to model it on an active-pixel CMOS ...
Zach's user avatar
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1 answer
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Transfer function and frequency of common drain Colpitts with ballast coil

Whilst looking for a circuit to test some unidentified RF filters and coils I have lying about, I came across a FET based common drain Colpitts used in this Youtube channel hosted by RF enthusiast ...
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Common drain / source follower stage circuit analysis

I have been recently working on different types of MOS amplifiers and the following are my main doubts, When we have a high gain stage such as the common source stage we use the output of this stage ...
Bhuvanesh Narayanan's user avatar
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Keysight's Advanced Design System users, what's wrong with this common drain circuit simulation?

For those of you that use Advanced Design System (ADS), from this circuit: Fundamental Frequency for transient simulation tool is set to 1 GHz. Yet, I'm getting this output: Main question: Since ...
kozner's user avatar
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2 answers
2k views

Common collector H-bridge driver - is there a way to do this with MOSFETs? Gate voltage seems too high

Background I made 4 of the following push pull circuits like the one below, to use as two H-bridge drivers for motors (stall current about 5A.) Sorry for not drawing the Darlingtons in full, I did ...
Level River St's user avatar
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Common drain amplifier vs op amp for unity gain (voltage Follower)

What is the difference between using a nFET vs. an op amp as a unity gain amplifier, i.e. voltage follower? Application: Provide constant voltage with a variable load, see example below: Min Current 0....
reaver shadow's user avatar
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6 answers
2k views

How is the current limited in this common drain circuit?

I'm trying to create a dummy load circuit, but it was limiting itself around 1.7 A, so I built this circuit. V1 is 0 - 5 V via a potentiometer, and V2 is a 5 V / 3 A power supply. simulate this ...
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