Datasheet

BIAS CIRCUITRY
20 k:
20 k:
V
+
- V
-
2
SUPPLY
MID-POINT
I TAIL
Q
2
Q
1
PIN 6
PIN 5
SD
PIN 2
V
-
V
+
PULL-UP
RESISTOR
20 k:
NOTE: PINS 2, 5, 6 ARE EXTERNAL
+
-
6.8 PF
C2
0.01 PF
R
IN
75:
R
G
560:
R
F
560:
C3
6.8 PF
C4
X1
-
+
R
OUT
75:
C1
0.01 PF
V
OUT
V
IN
-5V
+5V
LMH6703
www.ti.com SNOSAF2D –FEBRUARY 2005–REVISED MARCH 2013
VIDEO PERFORMANCE
Figure 31. Typical Video Application
The LMH6703 has been designed to provide excellent performance with production quality video signals in a
wide variety of formats such as HDTV and High Resolution VGA. NTSC and PAL performance is nearly flawless
with DG of 0.01% and DP of 0.02°. Best performance will be obtained with back terminated loads. The back
termination reduces reflections from the transmission line and effectively masks transmission line and other
parasitic capacitance from the amplifier output stage. Figure 31 shows a typical configuration for driving 75Ω
cable. The amplifier is configured for a gain of two compensating for the 6 dB loss due to R
OUT
.
ENABLE/DISABLE
Figure 32. SD Pin Simplified Schematic
(SOT-23 Pinout Shown)
For ±5V supplies only the LMH6703 has a TTL logic compatible disable function. Apply a logic low (< 0.8V) to
the SD pin and the LMH6703 is disabled. Apply a logic high (> 2.0V), or let the pin float and the LMH6703 is
enabled. Voltage, not current, at the Shutdown pin (SD) determines the enable/disable state. Care must be
exercised to prevent the shutdown pin voltage from going more than 0.8V below the midpoint of the supply
voltages (0V with split supplies, V
+
/2 with single supply biasing). Doing so could cause transistor Q1 to Zener
resulting in damage to the disable circuit (See Figure 32). The core amplifier is unaffected by this, but the
shutdown operation could become permanently slower as a result.
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