Anonymous
Anonymous asked in Science & MathematicsEngineering · 1 month ago

A direct coupled BJT preamp will have a flatter response, lower noise than capacitive coupled, T or F, why?

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  • qrk
    Lv 7
    1 month ago
    Favourite answer

    Flatter response at low frequencies because the series capacitance acts like a high-pass filter with the input impedance of the amplifier (input Z includes the bias network and input Z of the amplifier).

    Lower noise at lower frequencies because the capacitive reactance increases. The current noise is multiplied by the input impedance which creates a voltage noise (different from the voltage noise of the amplifier).

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  • 1 month ago

    TRUE !!!!!!!!!!!

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  • 1 month ago

    re noise: no, the only difference is in the very low frequency response, where noise is very low, unmeasurable compared to that at upper frequencies. 

    re frequency response, the DC coupled amp will have a flatter response at low frequencies, but at high frequencies they will be the same, all other things being equal.Noise is mostly due to the transistors, resistors, and other circuit elements. 

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  • 1 month ago

    No. If it has a capacitive coupling then it is not direct coupled.

    The question is moot.

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  • 1 month ago

    I don't even know what that is

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