Gain of TS922

[TomRett]

Hi, im trying to find out the gain from the TS922EIJT used inside the STEVAL-STWINKT1B evaluation board. Here is where the opamp is used.

So far, i have simulated the schematic using LTSpice and got a gain of -80 dB (see attached screenshot of the circuit)

Is this gain correct? I saw the open loop characteristics inside the documentation of this opamp and this here looks nothing like it. Since im calibrating my system i have to know the gain of this opamp. Is the unit in dBV or dB? And if it is in dBV, is it normalized to dB re 1V/Pa?

[AScha.3]

dont know, what you simulate... 🙂

the opamp has 100k/4k7 feedback , ~ 20x , or 26 dB .  ( dB is used for gain ; dBV for Voltage )

[LCE]

AScha.3 got it.

Anyway, I think I've seen some years ago that drawing opamps like this (square with pins) is IEEE-something conform, but honestly, it is TERRIBLE! It took more than the usual one glance to see it's just a voltage follower and an non-inverting (edited) amp... 😉
Getting old... (?)

[TomRett]

My calibration signal produces 94 dBSPL @1kHz which causes this mic to produce a -38dBV +-1. This number (-38dBV) is then added with the gain of the opamp (26 dB) which is -12 dBV +-1 (at this point that number irritates me). However, this is not what im measuring with the STWINKT1B-EVAL. Instead i get a peak at approx. -51 dBV which should be -38 dBV. A difference of approx. 13 dBV. Am i missing something that i have to consider in order to get the -38 dBV? 

[AScha.3]

>Am i missing something

yes - check with a scope , what you have really there !

1. the mic level...see ~  10mV ?

2. after amp, at cpu pin : see ~ 200 mV ?