# 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").

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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 ...
128 views

### 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 ...
278 views

### 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 ...
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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} ...
1 vote
890 views

### 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 – ...
47 views

### I would like to know if the circuit is correct?

simulate this circuit – Schematic created using CircuitLab I have used the voltage follower concept in order to keep the output logic non-inverted.I would like to know the issues that I might ...
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806 views

### 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. ...
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105 views

### 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 ...
1 vote
116 views

### 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 ...
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142 views

### How can I reduce loading effect in dc common drain source follower?

I want to make a dc voltage buffer using an nmos source follower. I found that by making Rs as large as possible or even open, Vs= Vgs-Vth. I verified it using multisim. The problem is it suffers from ...
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73 views

### Can I use a source follower to read the floating gate voltage then add a fixed tunneling voltage, then feed it back to the tunneling electrode?

So I was reading this research paper: H. Kosaka, T. Shibata, H. Ishii, and T. Ohmi, “An excellent weightupdating-linearity synapse memory cell for self-leaming neuron MOS neural networks,” in IEDM ...
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604 views

### CMOS source follower with 2 in series

I am really struggling with where to start to analyse this. Using the Shichman Hodges Model and the small signal equivalent circuit, the voltage gain can be equation can be seen to be vo = -gmvgsr0. ...
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2k views

### What are the advantages and uses of a voltage follower circuit over emitter follower?

Can I use a voltage follower and emitter follower for same purpose?
1 vote
891 views

### 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 ...
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### Stability problem OpAmp and FET source follower

I just found this site and read a few great interesting articles but nothing that would solve my problem I am hunting since a while. I have a OpAmp circuit with a N-FET source follower that regulates ...
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1k views

### 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 ...
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445 views

### Follower current source?

I need advice on a problem I'm having I need a follower to transmit an AC signal into a low impedance load which is the cathode of a triode but I also need it to be an adjustable current source to ...
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