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EL2073C
200MHz Unity-Gain Stable Operational Amplifier
E
L
20
73
C
Applications Information
Product Description
The EL2073C is a wideband monolithic operational
amplifier built on a high-speed complementary bipolar
process. The EL2073C uses a classical voltage-feedback
topology which allows it to be used in a variety of appli-
cations where current-feedback amplifiers are not
appropriate because of restrictions placed upon the feed-
back element used with the amplifier. The conventional
topology of the EL2073C allows, for example, a capaci-
tor 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
EL2073C is an excellent choice for applications such as
log amplifiers.
The EL2073C also has excellent DC specifications:
200V, VOS, 2A IB, 0.1A IOS, and 90dB of CMRR.
These specifications allow the EL2073C to be used in
DC-sensitive applications such as difference amplifiers.
Furthermore, the current noise of the EL2073C is only
3.2 pA/Hz, making it an excellent choice for high-sensi-
tivity transimpedance amplifier configurations.
Gain-Bandwidth Product
The EL2073C has a gain-bandwidth product of
200MHz. 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
bandwidths. For example, the EL2073C has a -3dB
bandwidth of 400MHz at a gain of +1, dropping to
200MHz at a gain of +2. It is important to note that the
EL2073C 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 EL2073C in a gain of +1 only exhibits 1dB
of peaking with a 100
load.
Video Performance
An industry-standard method of measuring the video
distortion of a component such as the EL2073C is to
measure the amount of differential gain (dG) and differ-
ential phase (dP) that it introduces. To make these
measurements, a 0.286VPP (40 IRE) signal is applied to
the device with 0V DC offset (0 IRE) at either 3.58MHz
for NTSC, 4.43MHz for PAL, or 30MHz for HDTV. 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 per-
cent. 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 (75
in series at the drive end, and 75 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 EL2073C has been designed to be among the best
video amplifiers in the marketplace today. It has been
thoroughly characterized for video performance in the
topology described above, and the results have been
included as minimum dG and dP specifications and as
typical performance curves. In a gain of +2, driving
150
, with standard video test levels at the input, the
EL2073C exhibits dG and dP of only 0.01% and 0.015°
at NTSC and PAL. Because dG and dP vary with differ-
ent DC offsets, the superior video performance of the
EL2073C 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.
The excellent output drive capability of the EL2073C
allows it to drive up to 4 back-terminated loads with
excellent video performance. With 4 150
loads, dG
and dP are only 0.15% and 0.08° at NTSC and PAL. For
more information, refer to the curves for Video Perfor-
mance vs Number of 150
Loads.
Output Drive Capability
The EL2073C has been optimized to drive 50
and 75
loads. It can easily drive 6VPP into a 50 load. This high
output drive capability makes the EL2073C an ideal
choice for RF, IF and video applications. Furthermore,