[damitamit]

Hi, im building my second MINT amp. The first had the standard resistor values giving a gain of 11.

This one is going to be used with grados so i was thinking a gain of 3-4.

Ive come up with these resistor values:

R3 - 470R
R4 - 1K
R5 - 1.5K
R6 - 470K

This gives a gain of 3.1 according to Tangents calculator.

Only thing is, im not sure if theres any rules the values have to adhere to such as certain resistors being bigger than others or somthing.

would these be ok? (before i order the values)

thanks
Amit

 

[tangent]

That'll be fine, as long as you're using an AD8620.

 

[damitamit]

ah. well i was thinking of using a OPA2228 for this one as i used a AD8620 for the last.

would i need to change the inner loop gain?

 

[tangent]

That inner loop gain is still fine for a 228, but the outer loop gain should be at least 5 with this chip.

 

[damitamit]

ah, ok tangent.

i shall use 220 for R3, giving a gain of 5.45

thanks!
(great board btw)

 

[tangent]

Just so you know, you're pressing your luck by going just barely over 5. If low gains are important to you, I'd switch to a different chip rather than skimp on gain.

Something you should consider: you can configure R1 and R2 in the amp to be an additional voltage divider beyond the volume control. If 5x gain is okay with you and 10x was too high, making R1==R2 will give you what you want while still allowing the amp to have a gain of 10.