So I am planning to use an AD620 instrumentation amplifier in my circuit. The gain formula is G = 1+(49.4KOhm/Rg), Rg being the deciding resistance value. By that logic if a 100K preset or Pot is set to zero, Gain attempted is (∞ + 1), which besides being impossible is also way above the 10000 max gain mentioned for this Instrumentation Amplifier. Would such a situation be safe for the amplifier or would it cook it up? What exactly happens in such situations?

 

Hi JS,
The usual action is to have 50R resistor in series with the Gain adjust post.

E

 

Hi JS,
The usual action is to have 50R resistor in series with the Gain adjust post. What is likely to happen with an infinite gain set?

E

Ah, of course

 

There will always be some residual resistance in the pot, so you will never get infinite gain. Even a large gain will not do anything any harm.
Note that a linear pot will give you a reciprocal-law gain control, which might not be the easiest to adjust. A series resistance (as @ericgibbs says) will also make the reciprocal law just a bit more linear.
The circuit as used in the AD620 is used in microphone preamplifiers, and it is conventional to use a reverse-log-law (C) potentiometer for gain adjustment.

 

There will always be some residual resistance in the pot, so you will never get infinite gain. Even a large gain will not do anything any harm.
Note that a linear pot will give you a reciprocal-law gain control, which might not be the easiest to adjust. A series resistance (as @ericgibbs says) will also make the reciprocal law just a bit more linear.
The circuit as used in the AD620 is used in microphone preamplifiers, and it is conventional to use a reverse-log-law (C) potentiometer for gain adjustment.

Got it. Thanks.