THS4130CDG4 Datasheet, PDF (13/36 Pages) Texas Instruments – HIGH-SPEED, LOW-NOISE, FULLY-DIFFERENTIAL I/O AMPLIFIERS

THS4130
THS4131
www.ti.com
APPLICATION INFORMATION
SLOS318H – MAY 2000 – REVISED MAY 2011
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
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_OCMpin, it is set to the midrail voltage
internally defined as:
ǒ Ǔ ǒ Ǔ VCC₎ ) VCC_–
2
(1)
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. Figure 29 shows the simplified diagram of the THS413x.
V_CC+
V_IN−
V_IN+
V_CC−
Vcm Error
Amplifier
+
_
Output Buffer
x1
C
R
C
R
x1
30 kΩ
Output Buffer
V_CC+
30 kΩ
V_CC−
V_OCM
Figure 29. THS413x Simplified Diagram
V_OUT+
V_OUT−
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