THS4130CDG4 Datasheet, PDF (17/36 Pages) Texas Instruments – HIGH-SPEED, LOW-NOISE, FULLY-DIFFERENTIAL I/O AMPLIFIERS

THS4130
THS4131
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PRINCIPLES OF OPERATION
SLOS318H – MAY 2000 – REVISED MAY 2011
THEORY OF OPERATION
The THS413x 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
THS413x
Fully differential Amplifier
V_CC+
V_IN−
_
+
V_O+
V_IN+
_
+
V_O−
V_OCM
V_CC−
Figure 35. Differential Amplifier Versus a Fully-Differential Amplifier
To understand the THS413x fully-differential amplifiers, the definition for the pin outs of the amplifier are
provided.
ǒ Ǔ ǒ Ǔ _{Input voltage definition VID + VI) – VI–}
VIC
+
ǒ_VI)Ǔ
)
2
ǒ_VI–Ǔ
(7)
ǒ Ǔ ǒ Ǔ Output voltage definition VOD + VO₎ – VO–
ǒ Ǔ _{VOC +}
VO₎
)
2
ǒVO–Ǔ
(8)
Transfer function
VOD + VID x A_ǒfǓ
(9)
Output common mode voltage VOC + VOCM
(10)
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 36. Definition of the Fully-Differential Amplifier
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