I am struggling with the following self-study problem, taken from The Analysis and Design of Linear Circuits (8th edition).
There are two things that shock me from this problem.
- We need to get a higher non inverting gain for the operational amplifier than the inverting gain. For me, this is hard to grasp because if the inverting gain is \$K = -\frac{R_2}{R_1}\$, then the non inverting gain will be \$K = a*(1+\frac{R_2}{R_1})\$, which is always lower than the inverting gain because a is a coefficient that can be added through voltage dividers (and thus \$a<1\$).
- How can you only have one operational amplifier, yet still get an amplification of -3 after the operational amplifier and before \$v_0\$?
Any guidance is tremendously appreciated. The book does not explain this at all and I am just a very confused student.
Edit:
The transfer function I computed is: $$V_A=5V_1 -V_2+V_0; V_0=-3V_A$$ $$V_0 = -15V_1 + 3V_2 - 3V_0 \Rightarrow V_0 = -3.75V_1 + 0.75V_2$$