EL2044C
EL2044C
Low Power/Low Voltage 120MHz Unity-Gain Stable Operational Amplifier
Applications Information
Product Description
The EL2044C is a low-power wideband monolithic
operational amplifier built on Elantec's proprietary high-
speed complementary bipolar process. The EL2044C
uses a classical voltage-feedback topology which allows
it to be used in a variety of applications where current-
feedback amplifiers are not appropriate because of
restrictions placed upon the feedback element used with
the amplifier. The conventional topology of the
EL2044C allows, for example, a capacitor to be placed
in the feedback 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 EL2044C is an
excellent choice for applications such as fast log
amplifiers.
60MHz at a gain of +2. It is important to note that the
EL2044C has been designed so that this “extra” band-
width in low-gain applications does not come at the
expense of stability. As seen in the typical performance
curves, the EL2044C in a gain of +1 only exhibits 1.0dB
of peaking with a 1000Ω load.
Video Performance
An industry-standard method of measuring the video
distortion of a component such as the EL2044C is to
measure the amount of differential gain (dG) and differ-
ential phase (dP) that it introduces. To make these
measurements, a 0.286V
PP
(40 IRE) signal is applied to
the device with 0V DC offset (0 IRE) at either 3.58MHz
for NTSC or 4.43MHz for PAL. A second measurement
is then made at 0.714V DC offset (100 IRE). Differential
gain is a measure of the change in amplitude of the sine
wave, and is measured in percent. Differential phase is a
measure of the change in phase, and is measured in
degrees.
For signal transmission and distribution, a back-termi-
nated cable (75Ω in series at the drive end, and 75Ω to
ground at the receiving end) is preferred since the
impedance match at both ends will absorb any reflec-
tions. However, when double termination is used, the
received signal is halved; therefore a gain of 2 configu-
ration is typically used to compensate for the
attenuation.
The EL2044C has been designed as an economical solu-
tion for applications requiring low video distortion. It
has been thoroughly characterized for video perfor-
mance in the topology described above, and the results
have been included as typical dG and dP specifications
and as typical performance curves. In a gain of +2, driv-
ing 150¾, with standard video test levels at the input, the
EL2044C exhibits dG and dP of only 0.04% and 0.15° at
NTSC and PAL. Because dG and dP can vary with dif-
ferent DC offsets, the video performance of the
EL2044C has been characterized over the entire DC off-
set range from -0.714V to +0.714V. For more
information, refer to the curves of dG and dP vs DC
Input Offset.
Single-Supply Operation
The EL2044C has been designed to have a wide input
and output voltage range. This design also makes the
EL2044C an excellent choice for single-supply opera-
tion. 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 300mV 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 sin-
gle 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 EL2044C still has 1V of output swing.
Gain-Bandwidth Product and the -3dB
Bandwidth
The EL2044C has a gain-bandwidth product of 60MHz
while using only 5.2mA of supply current. For gains
greater than 4, its closed-loop -3dB bandwidth is
approximately equal to the gain-bandwidth product
divided by the noise gain of the circuit. For gains less
than 4, higher-order poles in the amplifier's transfer
function contribute to even higher closed loop band-
widths. For example, the EL2044C has a -3dB
bandwidth of 120MHz at a gain of +1, dropping to
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ELANTEC [ ELANTEC SEMICONDUCTOR ]
