THS4140 Datasheet, PDF (15/24 Pages) Texas Instruments – HIGH SPEED FULLY DIFFERENTIAL I/O AMPLIFIERS

THS4140, THS4141
HIGHĆSPEED FULLY DIFFERENTIAL I/O AMPLIFIERS
SLOS320E − MAY 2000 − REVISED JANUARY 2004
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
Rf
R(g)
_
R(g)
+
Rf
THS414x
Fully differential Amplifier
VCC+
VIN−
_
+
VIN+
_
+
VO+
VO−
VOCM
VCC−
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
ǒ Ǔ ǒ Ǔ _{Output voltage definition VOD + VO) – VO–}
VOC
+
ǒ_VO)Ǔ ₎
2
ǒ_VO–Ǔ
Transfer function
VOD + VID x A_ǒfǓ
Output common mode voltage VOC + VOCM
Differential Structure Rejects
Coupled Noise at the Input
VCC+
VIN−
_
+
VIN+
_
+
Differential Structure Rejects
Coupled Noise at the Output
VO+
VO−
Differential Structure Rejects
Coupled Noise at the Power Supply
VOCM
VCC−
Figure 28. Definition of the Fully Differential Amplifier
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