Hi everyone,(adsbygoogle = window.adsbygoogle || []).push({});

I am trying to learn about circuits from some slides I obtained and I am stuck on a slide.

Here is a screenshot of it (it is in German): http://i.imgur.com/HCtWF.png

It says: Example: Illustration of maximum achievable amplification of a MOSFET with the use of the parameters g_{m}(transconductance) and g_{DS}(output conductance).

On the left is the circuit configuration. On the right is the effect of an input voltage change with x-axis drain voltage and y-axis drain current. It also has the derivation for the amplification.

What confuses me is how they obtained:

g_{m}* ΔU_{GS}+ g_{DS}* ΔU_{DS}= 0

as a result of I_{0}being constant. Perhaps I am not understanding the graph completely. Can someone point me in the correct direction?

For reference:

g_{m}= dI_{D}/ dU_{G}with U_{D}const.

g_{DS}= dI_{D}/ dU_{D}with U_{G}const.

Many thanks.

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# MOSFET Small-Signal Amplification

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