Page 851 - Mechanical Engineers' Handbook (Volume 2)

842 Mechatronics

R
V out ƒ
(52)
R
V in
Notice that for the inverting amplifier the gain is negative—hence the name ‘‘inverting.’’
This means that for periodic signals there would be a 180 phase shift between the output
voltage and the input voltage. The gain for this circuit is
A
R
ƒ
R (53)
V out AV in (54)

2.2 Noninverting Amplifier
Kirchhoff’s current law yields
i i out (55)
in
since i i 0. Kirchhoff’s voltage law yields

V Ri 0 (56)
in
V out Ri V 0 (57)
in
ƒ
V
i in (58)
R
V V
i in out (59)
R
ƒ
Setting the i’s equal gives
V V V
in in out (60)
R R ƒ
Dividing by V yields
in
R ƒ V out
1 (61)
R V in

R f i out

R i in
–

+ V out
+
V in
–

Note: Current here is not generally zero.
Figure 28 Noninverting operational amplifier.