EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
EL2150C/EL2157C June 1996 Rev B
Features
# Specified fora3V,a5V, or
g
5V Applications
# Power Down to 0 mA (EL2157C)
# Output Voltage Clamp
(EL2157C)
# Large Input Comon Mode Range
0V
k
k
V
CM
Vs - 1.2V
# Output Swings to Ground
Without Saturating
b
#
3 dB Bandwidthe125 MHz
g
#
0.1 dB Bandwidthe30 MHz
# Low Supply Current
# Slew Rate
e
275V/ms
# Low Offset Voltage
e
5mA
e
2mVmax
(PDIP and SO Packages)
e
# Output Current
# High Open Loop Gain
# Differential Gain
# Differential Phase
g
e
e
100 mA
e
0.05%
0.05
80 dB
§
Applications
# Video Amplifier
# PCMCIA Applications
# A/D Driver
# Line Driver
# Portable Computers
# High Speed Communications
# RGB Applications
# Broadcast Equipment
# Active Filtering
General Description
The EL2150C/EL2157C are the electronics industry’s fastest
single supply op amps available. Prior single supply op amps
have generally been limited to bandwidths and slew rates (/4
that of the EL2150C/EL2157C. The 125 MHz bandwidth,
275 V/ms slew rate, and 0.05%/0.05
tial phase makes this part ideal for single or dual supply video
speed applications. With its voltage feedback architecture, this
amplifier can accept reactive feedback networks, allowing them
to be used in analog filtering applications. The inputs can sense
signals below the bottom supply rail and as high as 1.2V below
the top rail. Connecting the load resistor to ground and operating from a single supply, the outputs swing completely to
ground without saturating. The outputs can also drive to within
1.2V of the top rail. The EL2150C/EL2157C will output
mA and will operate with single supply voltages as low as 2.7V,
making it ideal for portable, low power applications.
The EL2157C has a high speed disable feature. Applying a low
logic level to this pin reduces the supply current to 0 mA within
50 ns. This is useful for both multiplexing and reducing power
consumption.
The EL2157C also has an output voltage clamp feature. This
clamp is a fast recovery (
k
7 ns) output clamp that prevents the
output voltage from going above the preset clamp voltage. This
feature is desirable for A/D applications, as A/D converters can
require long times to recover if overdriven.
For applications where board space is critical the EL2150C is
available in the tiny 5 lead SOT23 package, which has a footprint 28% the size of an 8 lead SOIC. The EL2150C/EL2157C
are also both available in 8 pin plastic DIP and SOIC packages.
All parts operate over the industrial temperature range of
b
40§Ctoa85§C. For dual, triple, or quad applications, contact
the factory.
differential gain/differen-
§
g
100
Ordering Information
Part No. Temp. Range Package Outline
EL2150CNb40§Ctoa85§C 8 Pin PDIP MDP0031
EL2150CSb40§Ctoa85§C 8 Pin SOIC MDP0027
EL2150CWb40§Ctoa85§C 5 Pin SOT23* MDP0038
EL2157CNb40§Ctoa85§C 8 Pin PDIP MDP0031
EL2157CSb40§Ctoa85§C 8 Pin SOIC MDP0027
*See Ordering Information section of
databook.
Note: All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a ‘‘controlled document’’. Current revisions, if any, to these
specifications are maintained at the factory and are available upon your request. We recommend checking the revision level before finalization of your design documentation.
©
1995 Elantec, Inc.
Ý
Connection Diagrams
EL2150C EL2157C EL2150C
SO, P-DIP SO, P-DIP SOT23-5
Top View
2150– 1
Top View
2150– 2
Top View
2150– 3
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Absolute Maximum Ratings
Supply Voltage between V
Input Voltage (IN
a
ENABLE, CLAMP) GND
Differential Input Voltage
,INb,
a
S
and GND
b
(T
0.3V, V
A
a
S
e
12.6V
a
g
25§C)
0.3V
6V
Power Dissipation See Curves
Storage Temperature Range
Ambient Operating Temperature Range
b
65§Ctoa150§C
b
40§Ctoa85§C
Operating Junction Temperature 150
§
Maximum Output Current 90 mA
Output Short Circuit Duration (note 1)
Important Note:
All parameters having Min/Max specifications are guaranteed. The Test Level column indicates the specific device testing actually
performed during production and Quality inspection. Elantec performs most electrical tests using modern high-speed automatic test
equipment, specifically the LTX77 Series system. Unless otherwise noted, all tests are pulsed tests, therefore T
Test Level Test Procedure
I 100% production tested and QA sample tested per QA test plan QCX0002.
II 100% production tested at T
III QA sample tested per QA test plan QCX0002.
IV Parameter is guaranteed (but not tested) by Design and Characterization Data.
V Parameter is typical value at T
T
MAX
and T
per QA test plan QCX0002.
MIN
e
25§C and QA sample tested at T
A
e
25§C for information purposes only.
A
e
25§C,
A
e
e
T
TA.
J
C
DC Electrical Characteristics
(Note 2) V
ea
5V, GNDe0V, T
S
Parameter Description Conditions Min Typ Max
V
OS
TCV
Offset Voltage PDIP and SOIC Packages
Offset Voltage Temperature Coefficient Measured from Tmin to Tmax 10 V mV/§C
OS
IB Input Bias Current V
I
OS
TCI
Input Offset Current V
Input Bias Current Temperature Coefficient Measured from Tmin to Tmax 50 V nA/§C
OS
PSRR Power Supply Rejection Ratio V
CMRR Common Mode Rejection Ratio VCMe0V toa3.8V 55 65 I dB
CMIR Common Mode Input Range 0 V
R
IN
C
IN
R
OUT
I
S,ON
I
S,OFF
Input Resistance Common Mode 1 2 I MX
Input Capacitance SOIC Package 1 V pF
Output Resistance Avea140VmX
Supply CurrentÐEnabled V
Supply CurrentÐShut Down V
PSOR Power Supply Operating Range 2.7 12.0 I v
A
e
25§C, V
CM
e
1.5V, V
e
1.5V, V
OUT
CLAMP
SOT23-5 Package
e
0V
IN
e
0V
IN
e
V
S
ENABLE
e
V
CLAMP
OPEN
ea
5V, V
ea
2.7V toa12V, 55 70 I dB
ENABLE
ea
5V, unless otherwise specified.
b
22ImV
b
33ImV
b
5.5b10 I mA
b
750 150 750 I nA
VCMe0V toa3.0V 55 70 I dB
PDIP Package 1.5 V pF
e
S
e
S
e
V
S
V
CLAMP
V
CLAMP
V
CLAMP
ea
ea
ea
12V, V
10V, V
12V, V
ENABLE
ENABLE
ENABLE
ea
12V 5 6.5 I mA
ea
0.5V 0 50 I mA
ea
0.5V 5 V mA
Test
Level
b
1.2 I V
S
Units
C
TABWIDE
TDis 3.8in
2
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
DC Electrical Characteristics
(Note 2) V
specified
ea
5V, GNDe0V, T
S
Parameter Description Conditions Min Typ Max
A
e
25§C, V
CM
Ð Contd.
ea
1.5V, V
OUT
ea
1.5V, V
CLAMP
ea
5V, V
ENABLE
ea
5V, unless otherwise
Test
Level
Units
PSOR Power Supply Operating Range 2.7 12.0 I V
AVOL Open Loop Gain V
V
OP
V
ON
I
OUT
I
OUT,OFF
V
IH-EN
V
IL-EN
I
IH-EN
I
IL-EN
V
OR-CL
V
ACC-CL
I
IH-CL
I
IL-CL
Positive Output Voltage Swing V
Negative Output Voltage Swing V
Output Current (Note 1) V
Output Current, Disabled V
ENABLE pin Voltage for Power Up Relative to GND pin 2.0 I V
ENABLE pin Voltage for Shut Down Relative to GND pin 0.5 I V
ENABLE pin Input Current-High (Note 3) V
ENABLE pin Input Current-Low (Note 3) V
Voltage Clamp Operating Range (Note 4) Relative to GND pin 1.2 V
CLAMP Accuracy (Note 5) V
CLAMP pin Input CurrentÐHigh V
CLAMP pin Input CurrentÐLow V
e
S
a
9V, R
V
OUT
e
R
L
V
OUT
e
R
L
ea
S
ea
V
S
e
V
S
e
V
S
ea
V
S
ea
S
e
V
S
e
V
S
e
S
e
V
S
ENABLE
e
S
e
S
ea
IN
V
CLAMP
e
S
ea
S
ea
V
CLAMP
L
ea
12V, V
e
1kXto GND
1.5V toa3.5V, 70 V dB
ea
2V to 65 80 I dB
OUT
1kXto GND
ea
1.5V toa3.5V, 60 V dB
150X to GND
12V, A
12V, A
g
5V, A
g
5V, A
3V, A
12V, A
g
5V, A
g
5V, A
g
5V, A
g
5V, A
V
CLAMP
V
CLAMP
V
CLAMP
12V, V
4V, R
ea
ea
V
ea
V
ea
V
ea
V
ea
V
ea
V
ea
V
ea
V
ea
V
ea
V
ea
0.5V 0 20 I mA
ea
ea
e
L
1.5V anda3.5V
ea
CLAMP
e
1, R
1kXto 0V 10.8 V V
L
e
1, R
150X to 0V 9.6 10.0 I V
L
e
1, R
1kXto 0V 4.0 V V
L
e
1, R
150X to 0V 3.4 3.8 I V
L
e
1, R
150X to 0V 1.8 1.95 I V
L
e
1, R
150X to 0V 5.5 8 I mV
L
e
1, R
1kXto 0V
L
e
1, R
150X to 0V
L
e
1, R
10X to 0V
L
e
1, R
50X to 0V
L
12V, V
ENABLE
12V, V
ENABLE
1kXto GND
ea
12V 340 410 I mA
ea
0.5V 0 1 I mA
b
4.0 V V
b
3.7b3.4 I V
g75g
100 I mA
g
60 V mA
OP
b
250 100 250 I mV
12V 12 25 I mA
ea
1.2V
b20b
15 I mA
IV
TDis 5.2in
3
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Closed Loop AC Electrical Characteristics
(Notes2&6)V
e
0X,R
R
F
ea
5V, GNDe0V, T
S
e
150X to GND pin, unless otherwise specified
L
Parameter Description Conditions Min Typ Max
BW
BW
b
3 dB Bandwidth (V
g
0.1 dB Bandwidth (V
GBWP Gain Bandwidth Product V
PM Phase Margin R
SR Slew Rate V
tR,t
Rise Time, Fall Time
F
OS Overshoot
t
PD
t
S
Propagation Delay
0.1% Settling Time V
0.01% Settling Time V
dG Differential Gain (Note 7) A
dP Differential Phase (Note 7) A
e
i
t
t
t
N
N
DIS
EN
CL
Input Noise Voltage fe10 kHz 48 V nV0Hz
Input Noise Current fe10 kHz 1.25 V pA0Hz
Disable Time (Note 8) 50 V ns
Enable Time (Note 8) 25 V ns
Clamp Overload Recovery 7 V ns
Note 1: Internal short circuit protection circuitry has been built into the EL2150C/EL2157C. See the Applications section.
Note 2: CLAMP pin and ENABLE pin specifications apply only to the EL2157C.
Note 3: If the disable feature is not desired, tie the ENABLE pin to the V
Note 4: The maximum output voltage that can be clamped is limited to the maximum positive output Voltage, or V
Voltage higher than V
or simply let the CLAMP pin float.
inactivates the clamp. If the clamp feature is not desired, either tie the CLAMP pin to the VSpin,
OP
Note 5: The clamp accuracy is affected by V
Note 6: All AC tests are performed on a ‘‘warmed up’’ part, except slew rate, which is pulse tested.
Note 7: Standard NTSC signal
Note 8: Disable/Enable time is defined as the time from when the logic signal is applied to the ENABLE pin to when the supply
current has reached half its final value.
e
OUT
OUT
e
e
e
25§C, V
A
400 mVp-p) V
400 mVp-p) V
and RL. See the Typical Curves Section and the Clamp Accuracy vs. VIN&RLcurve.
IN
ea
1.5V, V
CM
ea
5V, A
S
ea
V
5V, A
S
ea
V
5V, A
S
ea
V
5V, A
S
ea
V
12V, A
S
ea
V
3V, A
S
ea
12V, A
S
ea
V
5V, A
S
ea
V
3V, A
S
ea
12V,@A
S
e
1kX,CLe6pF 55 V
L
ea
10V, R
S
ea
V
5V, R
S
g
0.1V step 2.8 V ns
g
0.1V step 10 V %
g
0.1V step 3.2 V ns
e
g
5V, R
S
e
g
5V, R
S
ea
2, R
V
ea
2, R
V
ea
1.5V, V
OUT
ea
1, R
0X 125 V MHz
V
eb
V
ea
V
ea
V
V
ea
V
V
ea
V
ea
V
L
e
L
e
L
e
L
e
1kX 0.05 V %
F
e
1kX 0.05 V
F
e
F
e
1, R
500X 60 V MHz
F
e
2, R
500X 60 V MHz
F
e
10, R
500X 6 V MHz
F
ea
e
1, R
0X 150 V MHz
F
e
1, R
0X 100 V MHz
F
ea
e
1, R
0X 25 V MHz
F
e
1, R
0X 30 V MHz
F
e
1, R
0X 20 V MHz
F
ea
10 60 V MHz
V
e
150X,V
150X,V
500X,A
500X,A
e
out
e
OUT
ea
V
ea
V
pin, or apply a logic high level to the ENABLE pin.
S
CLAMP
ea
5V, V
ENABLE
ea
0V toa6V 200 275 I V/ms
0V toa3V 300 V V/ms
e
1, V
1, V
g
3V 40 V ns
OUT
e
g
3V 75 V ns
OUT
286 mVp-p, fe3.58MHz, as VIN is swept from 0.6V to 1.314V. RLis DC coupled.
5V, A
Test
Level
. Applying a
OP
ea
V
Units
§
§
1,
TDis 5.1in
4
Typical Performance Curves
Non-Inverting
Frequency Response (Gain) Frequency Response (Phase)
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Non-Inverting
3 dB Bandwidth vs
Temperature for
Non-Inverting Gains
Inverting Frequency
Response (Gain)
Frequency Response
for Various R
L
Inverting Frequency
Response (Phase)
Frequency Response
for Various C
L
3 dB Bandwidth vs
Temperature for
Inverting Gains
Non-Inverting
Frequency Response vs
Common Mode Voltage
2150– 74
5
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
3 dB Bandwidth vs
Supply Voltage for
Non-Inverting Gains A
3 dB Bandwith vs Supply
Voltage for Inverting Gains
Ð Contd.
Frequency Response for
Various Supply Voltages,
ea
1
V
Frequency Response for
Various Supply Voltages,
ea
2
A
V
PSSR and CMRR
vs Frequency
PSRR and CMRR vs
Die Temperature
Open Loop Gain and
Phase vs Frequency
Open Loop Voltage Gain
vs Die Temperature
6
Closed Loop Output
Impedance vs Frequency
2150– 75
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
Large Signal Step Response,
ea
V
3V
S
Small Signal Step Response V
Ð Contd.
Large Signal Step Response,
ea
V
5V
S
Large Signal Step Response,
e
S
Large Signal Step Response,
ea
V
12V
S
g
5V
Slew Rate vs Temperature Settling Accuracy
Settling Time vs
Voltage and Current Noise
vs Frequency
2150– 76
7
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
Differential Gain for
Single Supply Operation Single Supply Operation
2nd and 3rd Harmonic
Distortion vs Frequency
Ð Contd.
Differential Phase for
2nd and 3rd Harmonic
Distortion vs Frequency
Differential Gain and Phase
for Dual Supply Operation
2nd and 3rd Harmonic
Distortion vs Frequency
Output Voltage Swing vs
Frequency for THD
k
0.1%
Output Voltage Swing vs
Frequency for Unlimited
Distortion
8
Output Current
vs Die Temperature
2150– 77
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
Supply Current vs
Supply Voltage Die Temperature
Offset Voltage vs
Die Temperature (4 Samples)
Ð Contd.
Supply Current vs
Input Bias Current
vs Input Voltage
Input Resistance vs
Die Temperature
Input Offset Current
and Input Bias Current
vs Die Temperature
Positive Output Voltage
Swing vs Die Temperature,
e
150X to GND
R
L
Negative Output Voltage
Swing vs Die Temperature,
e
R
150X to GND
L
9
Clamp Accuracy
vs Die Temperature
2150– 78
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
Clamp Accuracy
e
R
150X
L
2150– 48
Enable Response for a
Family of DC Inputs
Ð Contd.
Clamp Accuracy
e
R
1kX
L
2150– 49
Disable Response for a
Family of DC Inputs
Clamp Accuracy
e
R
10 kX
L
2150– 50
Disable/Enable Response for a
Family of Sine Waves
2150– 51
2150– 53
2150– 52
OFF Isolation
2150– 72
10
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Typical Performance Curves
5-Lead Plastic SOT23
Maximum Power Dissipation
vs Ambient Temperature
2150– 54
Burn-In Circuit
Ð Contd.
8-Lead Plastic DIP
Maximum Power Dissipation
vs Ambient Temperature
2150– 55
8-Lead Plastic SO
Maximum Power Dissipation
vs Ambient Temperature
2150– 57
2150– 56
Simplified Schematic
2150– 58
11
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Product Description
The EL2150C/EL2157C are the industry’s fastest
single supply operational amplifiers. Connected
in voltage follower mode, their
is 125 MHz while maintaining a 275 V/ms slew
rate. With an input and output common mode
range that includes ground, these amplifiers were
optimized for single supply operation, but will
also accept dual supplies. They operate on a total
supply voltage range as low as
a
12V. This makes them ideal fora3V applica-
tions, especially portable computers.
While many amplifiers claim to operate on a single supply, and some can sense ground at their
inputs, most fail to truly drive their outputs to
ground. If they do succeed in driving to ground,
the amplifier often saturates, causing distortion
and recovery delays. However, special circuitry
built into the EL2150C/EL2157C allows the output to follow the input signal to ground without
recovery delays.
Power Supply Bypassing And Printed
Circuit Board Layout
As with any high-frequency device, good printed
circuit board layout is necessary for optimum
performance. Ground plane construction is highly recommended. Lead lengths should be as short
as possible. The power supply pins must be well
bypassed to reduce the risk of oscillation. The
combination of a 4.7 mF tantalum capacitor in
parallel with a 0.1 mF ceramic capacitor has been
shown to work well when placed at each supply
pin. For single supply operation, where pin 4
(V
) is connected to the ground plane, a single
b
S
4.7 mF tantalum capacitor in parallel with a 0.1
mF ceramic capacitor across pins 7 and 4 will suffice.
For good AC performance, parasitic capacitance
should be kept to a minimum. Ground plane construction should be used. Carbon or Metal-Film
resistors are acceptable with the Metal-Film resistors giving slightly less peaking and bandwidth because of their additional series inductance. Use of sockets, particularly for the SO
package should be avoided if possible. Sockets
add parasitic inductance and capacitance which
will result in some additional peaking and overshoot.
b
3dB bandwidth
a
2.7V or up to
Supply Voltage Range and
Single-Supply Operation
The EL2150C/EL2157C have been designed to
operate with supply voltages having a span of
greater than 2.7V, and less than 12V. In practical
terms, this means that the EL2150C/EL2157C
will operate on dual supplies ranging from
g
1.35V tog6V. With a single-supply, the
EL2150C/EL2157C will operate from
a
12V. Performance has been optimized for a sin-
a
gle
5V supply.
Pins 7 and 4 are the power supply pins. The positive power supply is connected to pin 7. When
used in single supply mode, pin 4 is connected to
ground. When used in dual supply mode, the negative power supply is connected to pin 4.
As supply voltages continue to decrease, it becomes necessary to provide input and output
voltage ranges that can get as close as possible to
the supply voltages. The EL2150C/EL2157C
have an input voltage range that includes the
negative supply and extends to within 1.2V of the
positive supply. So, for example, on a single
supply, the EL2150C/EL2157C have an input
range which spans from 0V to 3.8V.
The output range of the EL2150C/EL2157C is
also quite large. It includes the negative rail, and
extends to within 1V of the top supply rail. On a
a
5V supply, the output is therefore capable of
swinging from 0V to
output will swing
to the negative rail and split supplies are used,
the output range is extended to the negative rail.
a
4V. On split supplies, the
g
4V. If the load resistor is tied
Choice Of Feedback Resistor, R
The feedback resistor forms a pole with the input
capacitance. As this pole becomes larger, phase
margin is reduced. This increases ringing in the
time domain and peaking in the frequency domain. Therefore, R
which should not be exceeded for optimum performance. If a large value of R
small capacitor in the few picofarad range in parallel with R
peaking at the expense of reducing the bandwidth.
12
can help to reduce this ringing and
F
has some maximum value
F
F
a
F
must be used, a
2.7V to
a
5V
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Ð Contd.
As far as the output stage of the amplifier is concerned, R
gains other than
a
RGappear in parallel with RLfor
F
a
1. As this combination gets
smaller, the bandwidth falls off. Consequently,
R
has a minimum value that should not be ex-
F
ceeded for optimum performance.
For A
b
ea
V
1ora2 (noise gain of 2), optimum response is
obtained with R
eb
Av
4ora5 (noise gain of 5), keep RFbe-
e
1, R
0X is optimum. For Av
F
between 500X and 1 kX. For
F
e
tween 2 kX and 10 kX.
Video Performance
For good video performance, an amplifier is required to maintain the same output impedance
and the same frequency response as DC levels are
changed at the output. This can be difficult when
driving a standard video load of 150X, because of
the change in output current with DC level. Differential Gain and Differential Phase for the
EL2150C/EL2157C are specified with the black
level of the output video signal set to
a
1.2V.
This allows ample room for the sync pulse even
in a gain of
and dP specifications of 0.05% and 0.05
driving 150X at a gain of
a
2 configuration. This results in dG
a
2. Setting the black
§
while
level to other values, although acceptable, will
compromise peak performance. For example,
looking at the single supply dG and dP curves for
e
R
150 X, if the output black level clamp is re-
L
duced from 1.2V to 0.6V dG/dP will increase
from 0.05%/0.05
gain of
a
2 configuration, this is the lowest black
to 0.08%/0.25§Note that in a
§
level allowed such that the sync tip doesn’t go
below 0V.
If your application requires that the output goes
to ground, then the output stage of the
EL2150C/EL2157C, like all other single supply
op amps, requires an external pull down resistor
tied to ground. As mentioned above, the current
flowing through this resistor becomes the DC
bias current for the output stage NPN transistor.
As this current approaches zero, the NPN turns
off, and dG and dP will increase. This becomes
more critical as the load resistor is increased in
value. While driving a light load, such as 1 kX,if
the input black level is kept above 1.25V, dG and
dP are a respectable 0.03% and 0.03
.
§
For other biasing conditions see the Differential
Gain and Differential Phase vs. Input Voltage
curves.
Output Drive Capability
In spite of their moderately low 5 mA of supply
current, the EL2150C/EL2157C are capable of
providing
load, or
g
100 mA of output current into a 10X
g
60 mA into 50X. With this large output
current capability, a 50X load can be driven to
g
3V with V
e
g
S
5V, making it an excellent
choice for driving isolation transformers in telecommunications applications.
Driving Cables and Capacitive Loads
When used as a cable driver, double termination
is always recommended for reflection-free performance. For those applications, the back-termination series resistor will de-couple the
EL2150C/EL2157C from the cable and allow extensive capacitive drive. However, other applications may have high capacitive loads without a
back-termination resistor. In these applications, a
small series resistor (usually between 5X and
50X) can be placed in series with the output to
eliminate most peaking. The gain resistor (R
G
can then be chosen to make up for any gain loss
which may be created by this additional resistor
at the output.
Disable/Power-Down
The EL2157C amplifier can be disabled, placing
its output in a high-impedance state. The disable
or enable action takes only about 40 nsec. When
disabled, the amplifier’s supply current is reduced to 0 mA, thereby eliminating all power
consumption by the EL2157C. The EL2157C amplifier’s power down can be controlled by standard CMOS signal levels at the ENABLE pin.
The applied CMOS signal is relative to the GND
pin. For example, if a single
the logic voltage levels will be
If using dual
b
be
4.5V andb3.0V. Letting the ENABLE pin
g
5V supplies, the logic levels will
a
5V supply is used,
a
0.5V anda2.0V.
float will disable the EL2157C. If the powerdown feature is not desired, connect the ENABLE pin to the V
levels of
levels of
a
0.5V anda2.0V are not standard TTL
a
0.8V anda2.0V, so care must be tak-
pin. The guaranteed logic
a
S
en if standard TTL will be used to drive the ENABLE pin.
)
13
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Ð Contd.
Output Voltage Clamp
The EL2157C amplifier has an output voltage
clamp. This clamping action is fast, being activated almost instantaneously, and being deactivated in
k
7 ns, and prevents the output voltage
from going above the preset clamp voltage. This
can be very helpful when the EL2157C is used to
drive an A/D converter, as some converters can
require long times to recover if overdriven. The
output voltage remains at the clamp voltage level
as long as the product of the input voltage and
the gain setting exceeds the clamp voltage. If the
EL2157C is connected in a gain of 2, for example,
a
and
3V DC is applied to the CLAMP pin, any
voltage higher than
clamped and
a
a
1.5V at the inputs will be
3V will be seen at the output.
Figure 1 below is a unity gain connected
EL2157C being driven by a 3Vp-p sinewave, with
2.25V applied to the CLAMP pin. The resulting
output waveform, with its output being clamped
to 2.25V, is shown in Figure 2.
Figure 1
2150– 59
Figure 3 shows the output of the same circuit
being driven by a 0.5V to 2.75V square wave, as
the clamp voltage is varied from 1.0V to 2.5V, as
well as the unclamped output signal. The rising
edge of the signal is clamped to the voltage applied to the CLAMP pin almost instantaneously.
The output recovers from the clamped mode
within5-7ns,depending on the clamp voltage.
Even when the CLAMP pin is taken 0.2V below
the minimum 1.2V specified, the output is still
clamped and recovers in about 11 ns.
Figure 3
2150– 61
The clamp accuracy is affected by 1) the CLAMP
pin voltage, 2) the input voltage, and 3) the load
resistor. Depending upon the application, the accuracy may be as little as a few tens of millivolts
to a few hundred millivolts. Be sure to allow for
these inaccuracies when choosing the clamp voltage. Curves of Clamp Accuracy vs. V
V
for 3 values of RLare included in the Typi-
IN
CLAMP
, and
cal Performance Curves Section
Unlike amplifiers that clamp at the input and are
therefore limited to non-inverting applications
only, the EL2157C output clamp architecture
works for both inverting and non-inverting gain
applications. There is also no maximum voltage
difference limitation between V
IN
and V
CLAMP
which is common on input clamped architectures.
Figure 2
2150– 60
The voltage clamp operates for any voltage be-
a
tween
mum output voltage swing, V
CLAMP pin much below
1.2V above the GND pin, and the mini. Forcing the
OP
a
1.2V can saturate
transistors and should therefore be avoided.
14
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Forcing the CLAMP pin above V
Ð Contd.
simply de-
OP
activates the CLAMP feature. In other words,
one cannot expect to clamp any voltage higher
than what the EL2157C can drive to in the first
place. If the clamp feature is not desired, either
let the CLAMP pin float or connect it to the V
S
pin.
EL2157C Comparator Application
The EL2157C can be used as a very fast, single
supply comparator by utilizing the clamp feature. Most op amps used as comparators allow
only slow speed operation because of output saturation issues. However, by applying a DC voltage
to the CLAMP pin of the EL2157C, the maximum output voltage can be clamped, thus preventing saturation. Figure 4 below is the
EL2157C implemented as a comparator. 2.5V DC
is applied to the CLAMP pin, as well as the IN
b
pin. A differential signal is then applied between
the inputs. Figure 5 shows the output square
wave that results when a
g
1V, 10 MHz triangular wave is applied, while Figure 6 is a graph of
propagation delay vs. overdrive as a square wave
is presented at the input.
Propagation Delay vs Overdrive
EL2157 as a Comparator
a
Figure 6
Video Sync Pulse Remover Application
All CMOS Analog to Digital Converters (A/Ds)
have a parasitic latch-up problem when subjected
to negative input voltage levels. Since the sync
tip contains no useful video information and it is
a negative going pulse, we can chop it off. Figure
7 shows a unity gain connected EL2150C/
EL2157C. Figure 8 shows the complete input video signal applied at the input, as well as the output signal with the negative going sync pulse removed.
2150– 64
Figure 4
Figure 5
2150– 62
2150– 65
Figure 7
2150– 63
15
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Figure 8
Ð Contd.
2150– 66
Multiplexing with the EL2157C
The ENABLE pin on the EL2157C allows for
multiplexing applications. Figure 9 shows two
EL2157Cs with their outputs tied together, driving a back terminated 75X video load. A 2 Vp-p
10 MHz sinewave is applied at one input, and a
1 Vp-p 5 MHz sinewave to the other. Figure 10
shows the CLOCK signal which is applied, and
the resulting output waveform at V
OUT
. Switching is complete in about 50 ns. Notice the outputs
are tied directly together. Decoupling resistors at
each output are not necessary. In fact, adding
them approximately doubles the switching time
to 100 nsec.
Figure 10
2150– 68
Short Circuit Current Limit
The EL2150C/EL2157C have internal short circuit protection circuitry that protect it in the
event of its output being shorted to either supply
rail. This limit is set to around 100 mA nominally
and reduces with increasing junction temperature. It is intended to handle temporary shorts. If
an output is shorted indefinitely, the power dissipation could easily increase such that the part
will be destroyed. Maximum reliability is maintained if the output current never exceeds
g
90 mA. A heat sink may be required to keep
the junction temperature below absolute maximum when an output is shorted indefinitely.
Power Dissipation
With the high output drive capability of the
EL2150C/EL2157C, it is possible to exceed the
150
C Absolute Maximum junction temperature
§
under certain load current conditions. Therefore,
it is important to calculate the maximum junction temperature for the application to determine
if power-supply voltages, load conditions, or
package type need to be modified for the
EL2150C/EL2157C to remain in the safe operating area.
Figure 9
2150– 67
16
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Ð Contd.
The maximum power dissipation allowed in a
package is determined according to[1]:
PD
MAX
e
i
JA
[1]
T
JMAX–TAMAX
where:
T
T
i
PD
JA
e
JMAX
AMAX
e
MAX
Maximum Junction Temperature
e
Maximum Ambient Temperature
Thermal Resistance of the Package
e
Maximum Power Dissipation in the
Package.
The maximum power dissipation actually produced by an IC is the total quiescent supply current times the total power supply voltage, plus
) *
V
]
OUT
R
L
[2]
the power in the IC due to the load, or[2
PD
MAX
e
VS*I
SMAX
a
(VS–V
OUT
where:
e
V
Total Supply Voltage
S
SMAX
OUT
e
Maximum Supply Current
e
Maximum Output Voltage of the Appli-
I
V
cation
e
R
Load Resistance tied to Ground
L
Single Supply Voltage
vs R
V
Single Supply Voltage
vs R
V
LOAD
(PDIP Package)
OUT
Figure 11
LOAD
(SO Package)
OUT
for Various
for Various
2150– 69
If we set the two PD
equal to each other, and solve for V
equations,[1]&[2],
MAX
S
, we can get a
family of curves for various loads and output
voltages according to[3]:
RL* (T
e
V
S
b
JMAX
T
i
JA
(IS* RL)aV
AMAX
)
a
OUT
(V
OUT
2
)
[3]
Figures 11 through 13 show total single supply
voltage V
vs. RLfor various output voltage
S
swings for the PDIP and SOIC packages. The
curves assume WORST CASE conditions of T
ea
85§C and I
S
e
6.5 mA.
Figure 12
Single Supply Voltage
vs R
V
A
17
for Various
LOAD
(SOT23-5 Package)
OUT
Figure 13
2150– 70
2150– 73
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
Applications Information
Ð Contd.
EL2157C Macromodel
* Revision A, July 1995 * Output Stage & Clamp
* When not being used, the clamp pin, pin 1, *
* should be connected to
* Connections:
*
*
*
*
*
*
.subckt EL2157/el 3 2 7 4 6 1
*
* Input Stage
*
i1 7 10 250uA
i2 7 11 250uA
r1 10 11 4k
q112210qp
q2 13 3 11 qpa
r2 12 4 100
r3 13 4 100
*
* Second Stage & Compensation
*
gm 15 4 13 12 4.6m
r4 15 4 15Meg
c1 15 4 0.36pF
*
* Poles
*
e1 17 4 15 4 1.0
r6 17 25 400
c3 25 4 1pF
r7 25 18 500
c4 18 4 1pF
*
a
Vsupply, pin 7 i3 20 4 1.0mA
a
input q3 7 23 20 qn
b
input
l
ll
lll
llll
lllll
a
Vsupply
b
Vsupply
output
clamp
llllll
q471819qn
q571821qn
q642022qp
q772318qn
d1 19 20 da
d2 18 1 da
r8 21 6 2
r9 22 6 2
r10 18 21 10k
r11 7 23 100k
d3 23 24 da
d4 24 4 da
d5 23 18 da
*
*Power Supply Current
*
ips 7 4 3.2mA
*
* Models
*
.model qn npn(is
.model qpa pnp(is
.model qp pnp(is
.model da d(tt
.ends
e
800e-18 bfe150 tfe0.02nS)
e
810e-18 bfe50 tfe0.02nS)
e
800e-18 bfe54 tfe0.02nS)
e
0nS)
TDis 3.8in
18
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
EL2157C Macromodel
Ð Contd.
2150– 71
19
EL2150C/EL2157C
125 MHz Single Supply, Clamping Op Amps
EL2150C/EL2157CJune 1996 Rev B
General Disclaimer
Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes
in the circuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any
circuits described herein and makes no representations that they are free from patent infringement.
WARNING Ð Life Support Policy
Elantec, Inc. products are not authorized for and should not be
used within Life Support Systems without the specific written
consent of Elantec, Inc. Life Support systems are equipment in-
Elantec, Inc.
1996 Tarob Court
Milpitas, CA 95035
Telephone: (408) 945-1323
(800) 333-6314
Fax: (408) 945-9305
European Office: 44-71-482-4596
tended to support or sustain life and whose failure to perform
when properly used in accordance with instructions provided can
be reasonably expected to result in significant personal injury or
death. Users contemplating application of Elantec, Inc. products
in Life Support Systems are requested to contact Elantec, Inc.
factory headquarters to establish suitable terms & conditions for
these applications. Elantec, Inc.’s warranty is limited to replacement of defective components and does not cover injury to persons or property or other consequential damages.
Printed in U.S.A.20
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