Op Amps for Everyone - The Repeater Builder's Technical ...

Simultaneous Equations
|m| 5.56 R F
(4–51)
R G
(4–52)
R F
5.56R G
Let R G = 10 kΩ, and then R F = 56.6 kΩ, which is not a standard 5% value, hence R F is
selected as 56 kΩ.
b V CC
R F R G
R G
R 1
R 1
R 2
1056 10 R 1
10 R 1
R 2
(4–53)
R 2
66–0.4444
0.4444 R 1 147.64R 1
(4–54)
The final equation for the example is given below
V OUT
5.56V IN
0.444
(4–55)
Select R 1 = 2 kΩ and R 2 = 295.28 kΩ. Since 295.28 kΩ is not a standard 5% resistor value,
R 1 is selected as 300 kΩ. The difference between the selected and calculated value of
R 1 has a nearly insignificant effect on b. The final circuit is shown in Figure 4–17, and the
measured transfer curve for this circuit is shown in Figure 4–18.
R F
56 kΩ
R G
10 k Ω
V CC = 10 V
0.01 µF
V IN
R 1
D1
_
+
V OUT
V CC = 10 V
R 2
2 kΩ
300 kΩ
0.01 µF
R L
10 kΩ
Figure 4–17. Case 3 Example Circuit
Single-Supply Op Amp Design Techniques
4-17