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  1. #1
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    Diode connected load or current mirror

    Hi

    I saw one figure of NMOS with current source. source source is replaced by diode connected load and in another circuit the current source is replaced by a current mirror. Which one is better. Can some one tell me the use of only diode connected load inplace of current source. (See attached figure, fig.1 is replaced by fig b or c

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  2. #2
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    Re: Diode connected load or current mirror

    It's a PMOS current source. their difference is their equivalent impedances. the diode connected load is simpler but it's small signal resistance is 1/gm (low impedance node) while for the one with a current mirror has a small signal resistance of ro (high impedance node). a higher impedance load gives a higher gain but needs a biasing circuit as shown. moreover, the diode connected load has a lower gain but is more linear because it's gain is dependent on the aspect ratio of the two transistors.



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