Page 304 - Mechatronics with Experiments

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would vary between
( 1 )
V = K diff V diff + ⋅ V common (5.200)
o
CMMR
5
V = 100 ⋅ (10 mV + (1∕10 ) ⋅ 0.0) = 1V; when V = 10 mV (5.201)
o
i
5
V = 100 ⋅ (10 mV + (1∕10 ) ⋅ 100 mV) = 1.0001 V (5.202)
o
; when V = (10 + 100) mV (5.203)
i
Clearly, the differential-ended signal and op-amp are able to amplify the desired portion of
the signal and attenuate very effectively the noise portion of the signal. The key assumption
for this to work is that the same noise signal is induced on both conductors (both inputs of
the differential amplifier).
5.6.2 Common Op-Amp Circuits

Op-amps are used in both open loop and closed loop configurations. Various op-amp
circuits for specific functions are discussed below: comparator, inverting and non-inverting
amplifier, sum, derivative, integral, and various filters.

Comparator Op-Amp The comparator functionality is to compare two signals, and
turn ON (i.e., V = V )orOFF(V =−V ) the output of the op-amp based on relative
o sat o sat
values of the two input signals (Figure 5.28). A reference signal V is connected to the
ref
inverting (−) input terminal. The other input signal (V ) is connected to the noninverting
i
(+) input terminal. The output of the op-amp will be either V = V or V =−V .The
o sat o sat
+V +V
V ref V - _ v 0 V i V - _ V 0

v i V + + R L V ref V + + R L
-V -V

V sat v i v 0 V sat v 0 v i

V ref V ref
Time Time

-V sat -V sat

v v
0 0
V sat V sat
slope = K 0 L

v i v i
V
-V sat ref -V sat V ref

FIGURE 5.28: Open loop op-amp used as a comparator: direct polarity and reverse polarity.