# OPA2836 View Datasheet(PDF) - Texas Instruments

 Part Name Description Manufacturer OPA2836 Very-Low-Power, Rail-to-Rail Out, Negative Rail In, Voltage-Feedback Operational Amplifiers Texas Instruments
OPA2836 Datasheet PDF : 59 Pages
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OPA836, OPA2836
SLOS712I – JANUARY 2011 – REVISED OCTOBER 2016
Application Information (continued)
Line termination on the output can be accomplished with resistors RO. The differential impedance seen from the
line will be 2 × RO. For example, if 100-Ω Cat5 cable is used with double termination, the amplifier is typically set
for a differential gain of 2 V/V (6 dB) with RF = 0 Ω (short), RG = open, 2R = 1 kΩ, R1 = 0 Ω, R = 499 Ω to
balance the input bias currents, and RO = 49.9 Ω for output line termination. This configuration is shown in
Figure 66.
For driving a differential-input ADC the situation is similar, but the output resistors, RO are selected with a
capacitor across the ADC input for optimum filtering and settling-time performance.
VSIG
VREF
VIN
½ OPA2836
+
RG
1 kΩ
RF
1 kΩ
49.9 Ω
VSIG
VOUT+ VREF
VREF
49.9 Ω
499 Ω
½ OPA2836
Figure 66. Cat5 Line Driver With Gain = 2 V/V (6 dB)
-VSIG
VOUT- VREF
9.1.6 Differential-to-Signal-Ended Amplifier
Figure 67 shows a differential amplifier that is used to convert differential signals to single-ended and provides
gain (or attenuation) and level shifting. This circuit can be used in applications like a line receiver for converting a
differential signal from a Cat5 cable to a single-ended signal.
If VIN+ = VCM + VSIG+ and VIN– = VCM + VSIG– , then the output of the amplifier may be calculated according to
Equation 5.
( ) VOUT =
VIN+
-
VIN-
´
æ
ç
RF
è RG
ö
÷
ø
+ VREF
(5)
G = RF
The signal gain of the circuit is
RG , VCM is rejected, and VREF provides a level shift around which the
output signal swings. The single ended output signal is in-phase with the differential input signal.
VSIG-
VCM
RG
VIN-
VIN+
RG
VCM
VSIG+
RF
RF
OPA 836
VOUT
G[(VSIG+)-(VSIG-)]
VREF
VREF
Figure 67. Differential to Single-Ended Amplifier
Line termination can be accomplished by adding a shunt resistor across the VIN+ and VIN- inputs. The
differential impedance is the shunt resistance in parallel with the input impedance of the amplifier circuit, which is
usually much higher. For low gain and low line impedance, the resistor value to add is approximately the
impedance of the line. For example if 100-Ω Cat5 cable is used with a gain of 1 amplifier and RF = RG = 1 kΩ,
adding a 100-Ω shunt across the input will give a differential impedance of 98 Ω, which is adequate for most
applications.