Datasheet
OPA836
V
IN+
V
IN-
V
CM
V
CM
R
G
R
G
R
F
R
F
V
REF
V
SIG-
V
SIG+
G[(V )-(
SIG
+
V )]
SIG-
V
OUT
V
REF
F
G
R
G =
R
( )
-
æ ö
- ´
ç ÷
è ø
F
OUT IN+ IN REF
G
R
V = V V + V
R
V
OUT+
49.9
+
V
OUT-
499
1k1k
OPA 836
+
V
REF
V
IN
V
SIG
V
REF
-V
SIG
V
REF
V
REF
V
SIG
OPA 836
49.9
OPA836
OPA2836
www.ti.com
SLOS712E –JANUARY 2011–REVISED SEPTEMBER 2013
Figure 56. CAT 5 Line Driver with Gain = 2 V/V (6 dB)
Differential to Signal Ended Amplifier
Figure 57 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 CAT 5 cable to single-ended.
If we set V
IN+
= V
CM
+ V
SIG+
and V
IN-
= V
CM
+ V
SIG-
, then
(4)
The signal gain of the circuit is set by: , V
CM
is rejected, and V
REF
provides a level shift around which
the output signal swings. The single ended output signal is in-phase with the differential input signal.
Figure 57. Differential to Single Ended Amplifier
Line termination can be accomplished with a resistor shunt across the input. The impedance seen differential
from the line will be the resistor value in parallel with the amplifier circuit. 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 R
F
= R
G
= 1 kΩ, adding a 100 Ω shunt across the input will give a differential
impedance of 98 Ω; this should be adequate for most applications.
For best CMRR performance, resistors must be matched. A rule of thumb is CMRR ≈ the resistor tolerance; so
0.1% tolerance will provide about 60 dB CMRR.
Differential to Differential Amplifier
Figure 58 shows a differential amplifier that is used to amplify differential signals. This circuit has high input
impedance and is often used in differential line driver applications where the signal source is a high impedance
driver like a differential DAC that needs to drive a line.
If we set V
IN±
= V
CM
+ V
SIG±
then
Copyright © 2011–2013, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Links: OPA836 OPA2836