EL2045C
Low-Power 100 MHz Gain-of-2 Stable Operational Amplifier
Burn-In Circuit
Gain-Bandwidth Product and the
b
3 dB
Bandwidth
The EL2045C has a gain-bandwidth product of
100 MHz while using only 5 2 mA of supply cur-
rent For gains greater than 4 its closed-loop
b
3 dB 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 EL2045C has a
b
3 dB
bandwidth of 100 MHz at a gain of
a
2 dropping
to 20 MHz at a gain of
a
5 It is important to
note that the EL2045C has been designed so that
this ‘‘extra’’ bandwidth in low-gain applications
does not come at the expense of stability As seen
in the typical performance curves the EL2045C
in a gain of
a
2 only exhibits 1 0 dB of peaking
with a 1000X load
2045 – 10
All Packages Use the Same Schematic
Applications Information
Product Description
The EL2045C is a low-power wideband gain-of-2
stable monolithic operational amplifier built on
Elantec’s proprietary high-speed complementary
bipolar process The EL2045C 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 topolo-
gy of the EL2045C 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 Similar-
ly because of the ability to use diodes in the feed-
back network the EL2045C is an excellent choice
for applications such as fast log amplifiers
Video Performance
An industry-standard method of measuring the
video distortion of a component such as the
EL2045C is to measure the amount of differential
gain (dG) and differential phase (dP) that it in-
troduces To make these measurements a
0 286 V
PP
(40 IRE) signal is applied to the device
with 0V DC offset (0 IRE) at either 3 58 MHz for
NTSC or 4 43 MHz for PAL A second measure-
ment 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 mea-
sured in percent Differential phase is a measure
of the change in phase and is measured in de-
grees
For signal transmission and distribution a back-
terminated cable (75X in series at the drive end
and 75X to ground at the receiving end) is pre-
ferred since the impedance match at both ends
will absorb any reflections However when dou-
ble termination is used the received signal is
halved therefore a gain of 2 configuration is typi-
cally used to compensate for the attenuation
The EL2045C has been designed as an economi-
cal solution for applications requiring low video
distortion It has been thoroughly characterized
Single-Supply Operation
The EL2045C has been designed to have a wide
input and output voltage range This design also
makes the EL2045C an excellent choice for sin-
gle-supply operation Using a single positive sup-
ply the lower input voltage range is within
100 mV of ground (R
L
e
500X) and the lower
output voltage range is within 300 mV of ground
Upper input voltage range reaches 4 2V and out-
put voltage range reaches 3 8V with a 5V supply
and R
L
e
500X 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 EL2045C still
has 1V of output swing
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ELANTEC [ ELANTEC SEMICONDUCTOR ]
