EL2245C, EL2445C
EL2245C, EL2445C
Dual/Quad Low-Power 100MHz Gain-of-2 Stable Op Amp
Applications Information
Product Description
The EL2245C/EL2445C are dual and quad low-power
wideband monolithic operational amplifiers built on
Elantec's proprietary high-speed complementary bipolar
process. The EL2245C/EL2445C use a classical volt-
age-feedback topology which allows them to be used in
a variety of applications where current-feedback ampli-
fiers are not appropriate because of restrictions placed
upon the feedback element used with the amplifier. The
conventional topology of the EL2245C/EL2445C
allows, for example, a capacitor to be placed in the feed-
back path, making it an excellent choice for applications
such as active filters, sample-and-holds, or integrators.
Similarly, because of the ability to use diodes in the
feedback network, the EL2245C/EL2445C are an excel-
lent choice for applications such as fast log amplifiers.
V
outmax
=Maximum Output Voltage Swing of the
Application
R
L
=Load Resistance
To serve as a guide for the user, we can calculate maxi-
mum allowable supply voltages for the example of the
video cable-driver below since we know that T
Jmax
=
150°C, T
max
= 75°C, I
Smax
= 7.6mA, and the package
θ
JA
s are shown in Table 1. If we assume (for this exam-
ple) that we are driving a back-terminated video cable,
then the maximum average value (over duty-cycle) of
V
outmax
is 1.4V, and R
L
= 150Ω, giving the results seen
in Table 1.
Table 1
Duals
EL2245CN
EL2245CS
QUADS
EL2445CN
EL2445CS
PDIP14
SO14
70°C/W
110°C/W
1.071W @ 75°C
0.682W @ 75°C
±11.5V
±7.5V
Package
PDIP8
SO8
θ
JA
95°C/W
150°C/W
Max PDiss
@ T
max
0.789W @ 75°C
0.500W @ 75°C
Max V
S
±16.6V
±10.7V
Power Dissipation
With the wide power supply range and large output drive
capability of the EL2245C/EL2445C, it is possible to
exceed the 150°C maximum junction temperatures
under certain load and power-supply conditions. It is
therefore important to calculate the maximum junction
temperature (T
Jmax
) for all applications to determine if
power supply voltages, load conditions, or package type
need to be modified for the EL2245C/EL2445C to
remain in the safe operating area. These parameters are
related as follows:
T
Jmax
= T
max
+ (θ
JA*
(PDmaxtotal))
where PDmaxtotal is the sum of the maximum power
dissipation of each amplifier in the package (PDmax).
PDmax for each amplifier can be calculated as follows:
PDmax= (2*V
S
*I
Smax
+(V
S
-V
outmax
)*(V
outmax
/R
L
))
where:
T
max
=Maximum Ambient Temperature
θ
JA
=Thermal Resistance of the Package
PDmax =Maximum Power Dissipation of 1 Amplifier
V
S
=Supply Voltage
I
Smax
=Maximum Supply Current of 1Amplifier
Single-Supply Operation
The EL2245C/EL2445C have been designed to have a
wide input and output voltage range. This design also
makes the EL2245C/EL2445C an excellent choice for
single-supply operation. Using a single positive supply,
the lower input voltage range is within 100mV of ground
(R
L
= 500Ω), and the lower output voltage range is
within 300 mV of ground. Upper input voltage range
reaches 4.2V, and output voltage range reaches 3.8V
with a 5V supply and R
L
= 500Ω. This results in a 3.5V
output swing on a single 5V supply. This wide output
voltage range also allows single-supply operation with a
supply voltage as high as 36V or as low as 2.5V. On a
single 2.5V supply, the EL2245C/EL2445C still have
1V of output swing.
Gain-Bandwidth Product and the -3dB
Bandwidth
The EL2245C/EL2445C have a bandwidth at gain-of-2
of 100MHz while using only 5.2mA of supply current
per amplifier. For gains greater than 4, their closed-loop
-3dB bandwidth is approximately equal to the gain-
9
ELANTEC [ ELANTEC SEMICONDUCTOR ]
