EL2245C, EL2445C
Dual/Quad Low-Power 100MHz Gain-of-2 Stable Op Amp
Applications Information
Voutmax =Maximum Output Voltage Swing of the
Application
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.
RL =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 TJmax
=
150°C, Tmax = 75°C, ISmax = 7.6mA, and the package
qJAs 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
Voutmax is 1.4V, and RL = 150W, giving the results seen
in Table 1.
Table 1
Duals
EL2245CN
EL2245CS
QUADS
Package
PDIP8
qJA
Max PDiss @ Tmax Max VS
95°C/W
150°C/W
0.789W @ 75°C
0.500W @ 75°C
±16.6V
±10.7V
SO8
Power Dissipation
EL2445CN
EL2445CS
PDIP14
SO14
70°C/W
1.071W @ 75°C
0.682W @ 75°C
±11.5V
±7.5V
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 (TJmax) 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:
110°C/W
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
(RL = 500W), 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 RL = 500W. 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.
TJmax = Tmax + (qJA* (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*VS*ISmax+(VS-Voutmax)*(Voutmax/RL))
where:
Tmax =Maximum Ambient Temperature
qJA =Thermal Resistance of the Package
PDmax =Maximum Power Dissipation of 1 Amplifier
VS =Supply Voltage
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-
ISmax =Maximum Supply Current of 1Amplifier
9
ELANTEC [ ELANTEC SEMICONDUCTOR ]
