Datasheet

2 µs/DIV
R
F
= R
G
= 1.3 k:
V
S
= ±5V
CONTROL
OUTPUT
0V
CONTROL
(2.5 V/DIV)
(2 V/DIV)
V
OUT
LMH6732
SNOSA47B –FEBRUARY 2003–REVISED MARCH 2013 www.ti.com
Figure 65. MUX “V
OUT
” and “Control” Waveform
DIFFERENTIAL GAIN AND PHASE
Differential gain and phase are measurements useful primarily in composite video channels. They are measured
by monitoring the gain and phase changes of a high frequency carrier (3.58MHz for NTSC and 4.43MHz for PAL
systems) as the output of the amplifier is swept over a range of DC voltages. Specifications for the LMH6732
include differential gain and phase. Test signals used are based on a 1V
PP
video level. Test conditions used are
the following:
DC sweep range: 0 to 100 IRE units (black to white)
Carrier: 4.43MHz at 40 IRE units peak to peak
A
V
= +2, R
L
= 75Ω + 75Ω
SOURCE IMPEDANCE
For best results, source impedance in the non-inverting circuit configuration (see Figure 59) should be kept below
5kΩ.
Above 5kΩ it is possible for oscillation to occur, depending on other circuit board parasitics. For high signal
source impedances, a resistor with a value of less than 5kΩ may be used to terminate the non-inverting input to
ground.
FEEDBACK RESISTOR
In current-feedback op amps, the value of the feedback resistor plays a major role in determining amplifier
dynamics. It is important to select the correct value. The LMH6732 provides optimum performance with feedback
resistors as shown in Table 2 below. Selection of an incorrect value can lead to severe roll-off in frequency
response, (if the resistor value is too large) or , peaking or oscillation (if the value is too low).
Table 2. Feedback Resistor Selection for Various Gain Settings and I
CC
’s
Gain (V/V) I
CC
(mA)
Unit
9 3.4 1
A
V
= +1 700 1k 1k Ω
A
V
= +2 700 1k 1k Ω
A
V
= −1 500 750 1k Ω
A
V
= −2 400 450 1k Ω
A
V
= [phone]k Ω
A
V
= −6 200 200 1k Ω
A
V
= +21 1k 1k 1k Ω
A
V
= −20 500 500 1k Ω
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