The configuration shown makes use of a simple source and the gain is given by the relationship between R3 and R1. The input impedance is on the order of 47 k and the output impedance is low. The voltage gain is 10 times, and this circuit is valid for other operational amplifiers of the same type. The 90k value is to obtain the exact gain of 10 times, but if a close gain is tolerated one can use 9.1k or even 100k, closer commercial values.
