Questions tagged [common-source]

A common source is one of the three basic FET topologies. It is distinguished by the fact that the input is at the FET's gate and the output is at the drain, leaving the FET's source as the "common" terminal. It typically exhibits high voltage gain but low bandwidth. Consider also using the "fet" or "mosfet" tag, as applicable.

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Why is the saturation region linear in the Vds v/s Vgs graph?

Looking at the problem mathematically, we see the equations $$I_\text{ds}=k_n'(V_\text{gs}-V_t)^2$$ $$V_\text{ds}=V_\text{dd}-I_\text{ds} \times R_o$$ Following this, it would be predictable that \$V_\...
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How to design a common source amplifier with active loading

I am quite new to amplifier. I want to design a common source amplifier. And here is my design in spice: Since the supply voltage is 6V. So i want my amplifier's operating point at 3V. So before i ...
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Calculation of power dissipation of a MOSFET circuit

As a part of an assignment to design a common source amplifier, I came up with this circuit: simulate this circuit – Schematic created using CircuitLab The transistor is a 180nm technology with ...
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Need help understanding current source loading common source amplifier

For the circuit in the diagram, I observe that Vgs is around 3V and so is Vds on the breadboard. I do not understand if it is necessary to keep the drain at 1/2 of V1 as it is done when using a drain ...
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Voltage swing limitation in CS stage diode connected load

According to this calculation, if Av(gain) is increased, Vds min(or Vo min) decreases which leads to an increase in voltage swing. But according to the book, I am referring to (Analog CMOS by Behzad ...
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Input capacitance of common source amplifier

I am trying to find the input capacitance for the common source amplifier stage below: - I have tried to find \$C_{in} \$ by simulation. I apply a linearly increasing voltage source \$v_{in}(t) = 1 \...
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Understanding the role of the FET in this opamp + Zener diode voltage regulator

I'm trying to repair my old audio CD player, and I've found a fault in or around this voltage regulator circuit (it's sourcing VCC for the DAC chip): I understand how the Zener + opamp work to ...
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Common Source MOSFET Amplifier Biasing

While reviewing simple transistor amplifier biasing techniques I came across this paragraph in Microelectronic Circuits by Sedra & Smith. Here too we show the \$i_D–v_{GS}\$ characteristics for ...
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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 ...
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common source pole calculation vs. simulation

I would like to compare my pole simulation results to my hand calculations. I'm receiving quite a big error. When simulating a common source stage without an output capacitance load there is a big ...
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Analysis of 3 stage common source ring oscillator

I have been attempting to analyze the following common source ring oscillator: I am having some trouble here. Based on my understanding, each stage of the FETs provides 270 degrees of phase shift ...
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Why should we set input source equal zero for calculating output resistance of common source amplifier?

This lecture (page 10) gave derivation of common source output resistance. What I don't quite get here is why we should set the input source equal 0 for calculating output resistance. Why?
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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 ...
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