# Large Signal Frequency Response

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#### ahmedsalah00

##### Member level 2
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 ?

#### Attachments

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

##### Super Moderator
Staff member
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.

ahmedsalah00

### ahmedsalah00

Points: 2

#### RCinFLA

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

#### ahmedsalah00

##### Member level 2
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

##### Super Moderator
Staff member
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.

ahmedsalah00

### ahmedsalah00

Points: 2

#### LvW

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).

ahmedsalah00

### ahmedsalah00

Points: 2

#### ahmedsalah00

##### Member level 2
Thanks so much for your feedback. It is much appreciated.

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