LT1187CS8#TR Linear Technology, LT1187CS8#TR Datasheet - Page 8

• Manufacturer Part Number: LT1187CS8#TR
• Description: IC AMP VID DIFF CURR FDBK 8SOIC
• Manufacturer: Linear Technology

Specifications of LT1187CS8#TR

• Applications: Differential
• Number Of Circuits: 1
• -3db Bandwidth: 50MHz
• Slew Rate: 165 V/µs
• Current - Supply: 13mA
• Current - Output / Channel: 20mA
• Voltage - Supply, Single/dual (±): 4.75 V ~ 16 V, ±2.38 V ~ 8 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Power Supply Requirement: Single/Dual
• Dual Supply Voltage (typ): ±5V
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
LT1187
The primary use of the LT1187 is in converting high speed
differential signals to a single-ended output. The LT1187
video difference amplifi er has two uncommitted high
input impedance (+) and (–) inputs. The amplifi er has
another set of inputs which can be used for reference and
feedback. Additionally, this set of inputs give gain adjust
and DC control to the difference amplifi er. The voltage
gain of the LT1187 is set like a conventional operational
amplifi er. Feedback is applied to Pin 8, and it is optimized
for gains of 2 or greater. The amplifi er can be operated
single-ended by connecting either the (+) or (–) inputs to
the +/REF (Pin 1). The voltage gain is set by the resistors:
(R
Like the single-ended case, the differential voltage gain is
set by the external resistors: (R
input differential signal for which the output will respond
is approximately ±0.38V.
V
8
IN DIFF
V
IN
FB
V
IN
+ R
3
2
1
8
3
2
1
8
R
R
G
G
G
+
–
–/FB
+
–
–/FB
+/REF
+/REF
S/D
S/D
)/R
LT1187
LT1187
V
5
5
A
O
V
V
V
R
V
V
R
G
= (V
+
–
FB
= +
+
–
FB
7
4
7
4
.
IN DIFF
R
FB
R
+
G
6
6
R
+ V
G
IN
V
V
)
OUT
OUT
R
FB
R
V
+
G
IN
R
G
FB
V
R
IN DIFF
G
V
V
+ R
O
IN
=
G
(
R
)/R
3
2
1
8
R
FB
3
2
1
8
G
R
+
–
+
+/REF
–/FB
G
+
–
S/D
–/FB
+/REF
R
S/D
G
LT1187
G
LT1187
5
. The maximum
A
5
(
V
V
V
V
R
R
V
V
= –
IN DIFF
+
–
FB
7
4
FB
+
–
7
4
R
FB
R
–
+
G
( (
6
R
R
6
R
LT1187 • AI01
FB
G
G
V
V
V
OUT
IN
OUT
Power Supply Bypassing
The LT1187 is quite tolerant of power supply bypassing.
In some applications a 0.1µF ceramic disc capacitor placed
1/2 inch from the amplifi er is all that is required. In ap-
plications requiring good settling time, it is important to
use multiple bypass capacitors. A 0.1µF ceramic disc in
parallel with a 4.7µF tantalum is recommended.
Calculating the Output Offset Voltage
Both input stages contribute to the output offset voltage at
Pin 6. The feedback correction forces balance in the input
stages by introducing an input V
expression for the output offset voltage is:
V
R
and R
DC reference voltage, for V
I
simplifi es to:
If R
tributes only 2mV, since I
OS
OUT
S
3
V
R
represents the input source resistance, typically 75Ω,
+
FB
is normally a small contributor and the expression
OUT
S
= (V
REF
is limited to 1k the last term of the equation con-
2
= V
R
OS
–
represents the fi nite source impedance from the
S
Figure 1. Simplifi ed Input Stage Schematic
Q1
OS
+ I
345 A
1.1k
(R
OS
R
E
FB
(R
Q2
S
+ R
) + I
G
+
B
)/R
(R
1 REF
B
R
REF
G
REF
is less than 2µA.
REF
+ I
)) • (R
grounded, R
Q3
B
OS
350 A
(R
1.1k
R
E
at Pin 8. The complete
FB
FB
Q4
)
+ R
G
7 V
4 V
)/R
REF
8
+
–
G
= 0Ω. The
+ I
R
B
G
ILT1187 • F01
(R
R
FB
6
1187fa
FB
)