Consider the circuit shown in Fig. 2.4 , which consists of one op amp and two resistors R1 and R2 .resistor R2 is connected from the out put terminal of the op amp, terminal 3, back to the inverting or negative input terminal, terminal 1. We speak of R2 as applying negative feedback. Note also that R2 close the loop around the op amp. In addition to adding R2 we have grounded terminal 2 and connected a resistor overall circuit is taken 1 and as input signal source with a voltage u1- The output of the overall circuit is taken at terminal 3 (that is, between terminal 3 and ground). Terminal 3 is, of course, a convenient point to take the output, since the impedance level there is ideally zero. Thus the voltage