Datasheet
V
-
(V)
-6 -5.5 -5 -4.5 -4 -3.5 -3
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
V
G
(V)
19.5
19.6
19.7
19.8
19.9
20
20.1
20.2
20.3
20.4
20.5
MAX GAIN
(
dB
)
V
G
MAX
MAX GAIN
V
G
LIMIT
V
+
= 5V
R
F
= 1k:
R
G
= 170:
-4.5 -4 -3.5 -3 -2.5 -2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
V
G
(V)
V
-
(V)
16.5
17
17.5
18
18.5
19
19.5
20
20.5
MAX GAIN
(
dB
)
V
G
MAX
MAX GAIN
V
G
LIMIT
V
+
= 2.5V
R
F
= 1k:
R
G
= 170:
LMH6503
www.ti.com
SNOSA78E –OCTOBER 2003–REVISED APRIL 2013
Table 1. V
G
Definition Based on V
−
V
G
Definition Expression (V)
V
G_MIN
Gain Cut-off 0.2 x V
−
V
G_MID
A
VMAX
/2 0
V
G_MAX
A
VMAX
−0.2 x V
−
b) V
G_LIMIT
(maximum permissible voltage on V
G
) is reduced. This is due to limitations within the device
arising from transistor headroom. Beyond this limit, device performance will be affected (non-destructive).
Referring to Figure 67, note that with V
+
= 2.5V, and V
−
= −4V, V
G_LIMIT
is approaching V
G_MAX
and already
"Max gain" is reduced by 1dB. This means that operating under these conditions has reduced the
maximum permissible voltage on V
G
to a level below what is needed to get Max gain. If supply voltages
are asymmetrical, reference Figure 67 and Figure 68 plots to make sure the region of operation is not
overly restricted by the "pinching" of V
G_LIMIT
, and V
G_MAX
curves.
c) "Max_gain" reduces. There is an intrinsic reduction in max gain when the total supply voltage is reduced
(see Figure 43). In addition, there is the more drastic mechanism described in "b" above and shown in
Figure 67.
Similar plots for V
+
= 5V operation are shown in Figure 68 for comparison and reference.
Figure 67. V
G_MAX
, V
G_LIMIT
, & Max-gain vs. V
-
(V
+
= 2.5V)
Figure 68. V
G_MAX
, V
G_LIMIT
, & Max-gain vs. V
-
(V
+
= 5V)
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