Datasheet

±I =
P
4R
M
1
´
2
1
n
2 V´
LPP
´
(9)
R
M
R
M
V
LPP
n
V
LPP
R
L
2V
LPP
n
V =
PP
Z =R
FB F
´
1+2 ´
R
L
R
S
+
R
P
R
S
1+2 ´
R
L
R
S
+
R
P
R
S
-
R
P
R
F
(12)
V =
PP 1 2
P
´V (V +V ) I (R +R )- -
CC
1 2
(10)
V =
CC 1 2
P
´V +(V +V )+I (R +R )
PP
1 2
(11)
R
G
C
M
100W
Z
LINE
R
F
R
F
1/4
THS6214
1/4
THS6214
R
M
R
S
R
S
R
P
R
P
V
IN
V
OUT
R
1
V
1
+V
CC
R
2
V
2
I
P
THS6214
SBOS431 – MAY 2009 ....................................................................................................................................................................................................... www.ti.com
As this turns ratio changes, the minimum allowed V
1
, V
2
, R
1
, and R
2
are given in Table 2 for ± 12V
supply voltage changes along with it. The peak operation.
current in the amplifier output is given by:
Table 2. Line Driver Headroom Model Values
V
1
R
1
V
2
R
2
± 12V 1V 0.6 Ω 1V 1.2 Ω
with V
PP
as defined in Equation 8 , and R
M
as defined
in Equation 3 and shown in Figure 83 .
When using a synthetic output impedance circuit (see
Figure 82 ), a significant drop is noticed in bandwidth
from the specification that appears in the Electrical
Characteristics tables. This apparent drop in
bandwidth for the differential signal is a result of the
apparent increase in the feedback transimpedance as
seen for each amplifier. This feedback
transimpedance equation is given below.
Figure 83. Driver Peak Output Voltage
To increase 0.1dB flatness to the frequency of
interest, adding a serial RC in parallel with the gain
With the previous information available, it is now
resistor may be needed, as shown in Figure 85 .
possible to select a supply voltage and the turns ratio
desired for the transformer, as well as calculate the
headroom for the THS6214.
The model, shown in Figure 84 , can be described
with the following set of equations:
1. As the available output swing:
2. Or as the required supply voltage:
The minimum supply voltage for power and load
requirements is given by Equation 11 .
Figure 85. +0.1dB Flatness Compensation Circuit
Figure 84. Line Driver Headroom Model
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