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how to test the bode graph

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achilles09

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bode graph

There is a buffer in a chip, I want to test it's bandwith ,but how to do it ?
Thank you all!
 

bodegraph

Do you mean that you want to measure the frequency response of the amplifier in the buffer? Because the gain through the buffer is going to be 1 up to the cutoff frequency. Not very interesting.

If you want to measure the amplifier, you need to somehow break the feedback loop and inject a test signal.
 

    achilles09

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snafflekid said:
Do you mean that you want to measure the frequency response of the amplifier in the buffer? Because the gain through the buffer is going to be 1 up to the cutoff frequency. Not very interesting.

If you want to measure the amplifier, you need to somehow break the feedback loop and inject a test signal.

no, the buffer is independently in a chip, i don't know how to test it's -3dB bandwith, which device i should use? thank you !
 

You apply a voltage sine wave generator to the input and measure what comes from the output. Increase the frequency until the Vrms output voltage equals half of the Vrms input voltage. That is the -3dB point.
 

snafflekid said:
You apply a voltage sine wave generator to the input and measure what comes from the output. Increase the frequency until the Vrms output voltage equals half of the Vrms input voltage. That is the -3dB point.

Thank you very much!:D
 

Hi,

You can use AC sweep for getting frequency response.

you can directly get the 3DB response by means of macros in PSpice.

bye
 

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