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  1. #1
    Member level 3
    Points: 1,622, Level: 9

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    Feb 2006
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    dc transient analysis

    Hi there,

    When we are doing circuit design, we always check our circuit by DC analysis, transient analysis, AC analysis and etc.

    As i know, DC analysis is meant to check for dc operating poing while DC analysis is meant for time-domain checking and AC analysis is meant for frequency-domain analysis.

    However, could anyone explain the purpose of DC analysis and transient analysis in a more intuitive way. Please kindly including what aspect we are checking and what are the purposes of the DC and transient analysis.

    Please kindly include the reason why we need to do dc analysis and transient analysis? What characteristic we may check by DC analysis but not tran analysis and vice versa.

    Thank you very much.

    •   Alt5th June 2009, 16:12



  2. #2
    Advanced Member level 5
    Points: 39,631, Level: 48
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    LvW's Avatar
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    May 2008
    1704 / 1704

    ac analysis vs transient analysis

    Well, I try a short explanation:

    1.) In dc analysis a voltage or a current or a global parameter (resistor, temperature) is swept - and the resulting voltage resp. current distribution in the nezwork is computet. Important: During this analysis all ac relevant parts (capacitor, inductor) are set to ZERO. This analysis is important for producing characteristic transfer curves like Ic=f(Vbe).

    2.) During TRAN analysis first an initial operating point is calculated (based on dc values) and after that all momentary voltages and currents are computed as the result of a time dependent voltage or current source - including, of course, the influence of capacitors and inductors as well as all non-linearities (clipping effects due to voltage limits etc.)

    3.) AC-analysis does NOT take into consideration any non-linearities. Based on the actual bias point the small signal behaviour is analyzed (using the slope of characteristic functions). Therefore, the input signal may be as large as you want (best choice: 1 volt or 1 amp).

    I hope this helpes and I didn´t forget some important points.

    5 members found this post helpful.

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