EL5144C, EL5146C, EL5244C, EL5246C,
EL5444C
100 MHz Single Supply Rail to Rail Amplifier
ISMAX = Maximum Supply Current Per Amplifier
VOUT = Maximum Output Voltage of the Application
RL = Load Resistance tied to Ground
If we set the two PDMAX equations equal to each other,
we can solve for RL:
RL=
-------------------V-----O----U----T-----•----(---V----S-----–----V-----O----U----T----)--------------------
T----J---M-----A-N---X---•--–--Θ---T--J--AA----M-----A----X--
–
(VS
•
ISMAX)
ure 4 is a graph of propagation delay vs. overdrive as a
square wave is presented at the input of the comparator.
1
8
EL5146C
VIN
+
–
2
-
7
+
3
6
+2.5V
4
5
+5V
0.1µF
VOUT
RL
Figure 3
Propagation Delay vs. Overdrive for Amplifier Used as a
8 Comparator
1000
Assuming worst case conditions of TA = +85°C, Vout =
VS/2 V, VS = 5.5V, and ISMAX = 8.8mA per amplifier,
below is a table of all packages and the minimum RL
allowed.
Part
EL5144CW
EL5146CS
EL5146CN
EL5244CS
EL5244CN
EL5244CY
EL5246CY
EL5246CS
EL5246CN
EL5444CU
EL5444CS
EL5444CN
Package
SOT23-5
SOIC-8
PDIP-8
SOIC-8
PDIP-8
MSOP-8
MSOP-10
SOIC-14
PDIP-14
QSOP-16
SOIC-14
PDIP-14
Minimum RL
37
21
14
48
30
69
69
34
23
139
85
51
EL5144C Series Comparator Application
The EL5144C series amplifier can be used as a very fast,
single supply comparator. Most op amps used as a com-
parator allow only slow speed operation because of
output saturation issues. The EL5144C series amplifier
doesn’t suffer from output saturation issues. Figure 3
shows the amplifier implemented as a comparator. Fig-
Negative Going Signal
100
Positive Going Signal
10
0.01
0.1
1.0
OVERDRIVE (V)
Figure 4
Multiplexing with the EL5144C Series
Amplifier
Besides normal power down usage, the CE (Chip
Enable) pin on the EL5146C and EL5246C series ampli-
fiers also allow for multiplexing applications. Figure 5
shows an EL5246C with its outputs tied together, driv-
ing a back terminated 75Ω video load. A 3 Vp-p 10 MHz
sine wave is applied at Amp A input, and a 2.4 Vp-p 5
MHz square wave to Amp B. Figure 6 shows the
SELECT signal that is applied, and the resulting output
waveform at VOUT. Observe the break-before-make
operation of the multiplexing. Amp A is on and VIN1 is
being passed through to the output of the amplifier. Then
Amp A turns off in about 10 nsec. The output decays to
18