THS4150CDGN Datasheet, PDF (13/34 Pages) Texas Instruments – HIGH-SPEED DIFFERENTIAL I/O AMPLIFIERS

THS4150
THS4151
www.ti.com........................................................................................................................................................... SLOS321G – MAY 2000 – REVISED MARCH 2009
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 resistors. 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:
ǒV Ǔ _CC) ) ǒVCC–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 when gain is 1. V_OCM has a high bandwidth capability up to the typical operating
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 30 shows the simplified diagram of the THS415x.
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 30. THS415x Simplified Diagram
V_OUT+
V_OUT-
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