Hello.

I have a question about gain set of SSM2304

There are two equations in the datasheet.

What is a correct equation? And When I calculated 376/47=8dB.

But, the default valueis 18dB. Is there any problem on that?

The first one is shown as below. you can find that page1 in the datasheet.

The second is shown as below.you can find that page12 in the datasheet.

The equation on page 12 of the data sheet is correct. The Zin of this amplifier is 47 kohm and it's default gain setting is 18 dB, leading to a 376 kohm feedback resistor. Note that your gain calculation is not correct. 376/47 = 8 gives you the linear gain of the amplifier, but not the gain in dB. To get the gain in dB, you need to take 20x the log of the linear gain: 18 dB = 20*log10(8).

The SSM2304 isn't recommended for new designs. If you are starting a new design, we recommend that you look at the SSM2306, which has the same gain setting and performs much better with a loaded output.