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| university:courses:electronics:electronics-lab-11m [26 Feb 2021 14:07] – Antoniu Miclaus | university:courses:electronics:electronics-lab-11m [07 Feb 2022 15:44] (current) – [Activity: The Source follower (NMOS)] Doug Mercer |
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| ====== Activity: The Source follower (NMOS)====== | ====== Activity: The Source follower (NMOS) - ADALM2000====== |
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| ===== Objective: ===== | ===== Objective: ===== |
| The incremental Gain (Vout /Vin) of the source follower should ideally be 1 but will always be slightly less than 1. The gain is generally given by the following equation: | The incremental Gain (Vout /Vin) of the source follower should ideally be 1 but will always be slightly less than 1. The gain is generally given by the following equation: |
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| From the equation we can see that in order to obtain a gain close to one we can either increase R<sub>L</sub> or decrease r<sub>s</sub>. We also know that r<sub>s</sub> is a function of I<sub>D</sub> and that as I<sub>D</sub> increases r<sub>s</sub> decreases. Also from the circuit we can see that I<sub>D</sub> is related to R<sub>L</sub> and that as R<sub>L</sub> increases I<sub>D</sub> decreases. These two effects work counter to each other in the simple resistive loaded emitter follower. Thus to optimize the gain of the follower we need to explore ways to either decrease r<sub>s</sub> or increase R<sub>L</sub> without effecting the other. It is important to remember that in MOS transistors I<sub>D</sub> = I<sub>S</sub> ( I<sub>G</sub> = 0 ). | From the equation we can see that in order to obtain a gain close to one we can either increase R<sub>L</sub> or decrease r<sub>s</sub>. We also know that r<sub>s</sub> is a function of I<sub>D</sub> and that as I<sub>D</sub> increases r<sub>s</sub> decreases. Also from the circuit we can see that I<sub>D</sub> is related to R<sub>L</sub> and that as R<sub>L</sub> increases I<sub>D</sub> decreases. These two effects work counter to each other in the simple resistive loaded source follower. Thus to optimize the gain of the follower we need to explore ways to either decrease r<sub>s</sub> or increase R<sub>L</sub> without effecting the other. It is important to remember that in MOS transistors I<sub>D</sub> = I<sub>S</sub> ( I<sub>G</sub> = 0 ). |
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| {{ :university:courses:electronics:a11m_e1.png?100 |}} | {{ :university:courses:electronics:a11m_e1.png?100 |}} |
