THS4140 Datasheet, PDF (15/33 Pages) Texas Instruments – HIGH SPEED FULLY DIFFERENTIAL I/O AMPLIFIERS

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THS4140
THS4141
SLOS320F – MAY 2000 – REVISED JANUARY 2006
PRINCIPLES OF OPERATION
THEORY OF OPERATION
The THS414x is a fully differential amplifier. Differential amplifiers are typically differential in/single out, whereas
fully differential amplifiers are differential in/differential out.
Differential Amplifier
R_f
R_(g)
_
+
R_(g)
R_f
THS414x
Fully differential Amplifier
V_CC+
V_IN-
_
+
V_O+
V_IN+
_
+
V_O-
V_OCM
V_CC-
Figure 27. Differential Amplifier Versus a Fully Differential Amplifier
To understand the THS414x fully differential amplifiers, the definition for the pinouts of the amplifier are
provided.
ǒ Ǔ ǒ Ǔ _{Input voltage definition VID + VI) – VI–}
VIC
+
ǒ_VI)Ǔ
)
2
ǒ_VI–Ǔ
(6)
ǒ Ǔ ǒ Ǔ Output voltage definition VOD + VO₎ – VO–
ǒ Ǔ ǒ Ǔ _{VOC +}
VO₎
)
2
VO–
(7)
Transfer function
VOD + VID x A_ǒfǓ
(8)
Output common mode voltage VOC + VOCM
(9)
Differential Structure Rejects
Coupled Noise at the Input
V_CC+
Differential Structure Rejects
Coupled Noise at the Output
V_IN-
_
+
V_O+
V_IN+
_
+
V_O-
Differential Structure Rejects
Coupled Noise at the Power Supply
V_OCM
V_CC-
Figure 28. Definition of the Fully Differential Amplifier
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