THS4130 Datasheet, PDF (19/27 Pages) Texas Instruments – HIGH SPEED LOW NOISE, FULLY DIFFERENTIAL I/O AMPLIFIERS

THS4130, THS4131
HIGHĆSPEED, LOW NOISE, FULLYĆDIFFERENTIAL I/O AMPLIFIERS
SLOS318E − MAY 2000 − REVISED JANUARY 2004
PRINCIPLES OF OPERATION
theory of operation (continued)
The following schematics depict the differences between the operation of the THS413x, fully differential
amplifier, in two different modes. Fully differential amplifiers can work with differential input or can be
implemented as single in/differential out.
Rf
VIN− ^R(g)
Vs
VIN+
R(g)
VCC+
−+
+−
VOCM
VCC−
VO+
VO−
Rf
Note: For proper operation, maintain symmetry by setting
Rf1 = Rf2 = Rf and R(g)1 = R(g)2 = R(g) ⇒ A = Rf/R(g)
Figure 37. Amplifying Differential Signals
VIN− ^R(g)
VIN+
Vs
R(g)
Rf
VCC+
−+
+−
VOCM
VCC−
VO+
VO−
RECOMMENDED RESISTOR VALUES
GAIN
1
2
5
10
R(g) Ω
390
374
402
402
Rf Ω
390
750
2010
4020
Rf
Figure 38. Single In With Differential Out
If each output is measured independently, each output is one-half of the input signal when gain is 1. The
following equations express the transfer function for each output:
VO
+
1
2
VI
The second output is equal and opposite in sign:
VO
+
–
1
2
VI
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