THS4130 Datasheet, PDF (14/27 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
APPLICATION INFORMATION
resistor matching
Resistor matching is important in fully differential amplifiers. The balance of the output on the reference voltage
depends on matched ratios of the resistor. CMRR, PSRR, and cancellation of the second harmonic distortion
will diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or better
to keep the performance optimized.
V_OCM sets the dc level of the output signals. If no voltage is applied to the V_OCM pin, it will be set to the midrail
voltage internally defined as:
ǒ_V
Ǔ
CC)
)
ǒ_VCC–Ǔ
2
In the differential mode, the V_OCM on the two outputs cancel each other. Therefore, the output in the differential
mode is the same as the input in the gain of 1. V_OCM has a high bandwidth capability up to the typical operation
range of the amplifier. For the prevention of noise going through the device, use a 0.1 µF capacitor on the V_OCM
pin as a bypass capacitor. The following graph shows the simplified diagram of the THS413x.
VCC+
VIN−
VIN+
VCC−
Vcm Error
Amplifier
+
_
Output Buffer
x1
C
R
C
R
30 kΩ
x1
Output Buffer
VCC+
30 kΩ
VCC−
VOCM
Figure 29. THS413x Simplified Diagram
VOUT+
VOUT−
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