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Large Signal Frequency Response

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ahmedsalah00

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Hi
I just need to understand the curve entiteled "Large Signal Frequency Response' in the AD620 Instrumentation amplifier datasheet.
my concrete questions are:
1- What are the dashed verticle lines ? G=100 and G=1000
2- What does the phrase "BW limit" indicate in the curve? and why ?

please find the datasheet attached.
 

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  • Figure 20. Large Signal Frequency Response.jpg
    Figure 20. Large Signal Frequency Response.jpg
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FvM

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The Large Signal Frequency Response diagram gives the maximum voltage that can be output due to limited slew rate of the amplifier. The dashed line shows the -3 dB bandwidth limit for different gains, as it't also shown in the gain vs. frequency graph.
 

RCinFLA

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There is a finite slew rate of the amplifier which limits the bandwidth at larger signals.
 

ahmedsalah00

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The Large Signal Frequency Response diagram gives the maximum voltage that can be output due to limited slew rate of the amplifier. The dashed line shows the -3 dB bandwidth limit for different gains, as it't also shown in the gain vs. frequency graph.


so , we may think of figure 20 as the SOA (safe operating area ) of work ?
 

FvM

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It's not a safe operation area but an area of linear amplifier operation. When the signal is affected by limited slew rate, a sine get's distorted to triangle.
 

LvW

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It's not a safe operation area but an area of linear amplifier operation. When the signal is affected by limited slew rate, a sine get's distorted to triangle.

Yes, but note: linear operation is always possible (that means: also for frequencies higher than the indicated BW limit) if the amplitudes remain within the limits as shown in the graph.

---------- Post added at 08:06 ---------- Previous post was at 07:42 ----------

As far as the vertical dashed lines are concerned: These are frequency limits (3-dB BW) caused by the small-signal behaviour of the circuit for two differnt gain values (see also Fig. 19 of the data sheet).
 
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