
9
EL1504C, EL1505C
Differential Line Driver
EL
1504C,
EL1505
C
The first term of the equation is the quiescent dissipation
and the second term is the dissipation due to both ampli-
fiers driving a load. If outputs are sinusoidal signals of
VO volts per amplifier peak-to-peak rather than DC the
dissipation is:
where RL refers to the load seen by one amplifier con-
nected in the differential configuration described in the
previous page. The following graphs refer to RLD which
is the differential load seen by both amplifiers.
The graph above shows the output current capability of a
differentially connected driver pair with different VS,
VOUT and RLD. The area between the horizontal, verti-
cal and diagonal lines represents the linear operating
region of the device. The upper horizontal line is the
maximum current handling capability of the device and
is limited by the linearity of the output transistors. The
vertical lines are the peak output voltage swings with
different supply voltages limited by clipping. The diag-
onal lines result from the series resistance of the output
transistors.
The graph above shows the peak power available as the
output swing is varied for different power supplies. The
different line styles represent the maximum power
which can be reached for a given supply voltage. The
dots delineate the ±5V, ±6V, and ±15V regions on each
curveIt is interesting to note that the 100
load and the
200
load cases both produce similiar power output for
a supply voltage of ±15V and that more power can be
obtained by using a 150
load. By referring back to the
first graph we can see that the 150
load would be the
best choice because that load line intersects the linear
P
D
2V
s
I
s
2
V
s
2
V
o
2
×
8
---------------------
V
s
V
o
3
×
3
π
--------------------
–
3V
o
4
×
128
----------------
+
R
L
----------------------------------------------------------------------------
×
+
×
=
DIFFERENTIAL PEAK VOUT (V)
I L
O
AD
(
m
A)
0
200
012
24
Load Lines for Various Loads
120
18
30
6
160
80
40
RLD = 50
RLD = 100
RLD = 150
RLD = 200
Linear Region
VMAX
IMAX
±15V
±5V
±6V
VOUT (V)
P
OU
T
(W
,pea
k)
0
0.8
3.6
0
8
16
28
Output Power for a Given Load
2.0
1.6
12
20
424
2.4
1.2
0.4
3.2
RLD = 150
RLD = 100
RLD = 200
±15V
Output Power
±6V
±5V
RLD = 50
2.8