EL2176CEL2276C

December

1995

Rev

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

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

Features

Single (EL2176C) and dual

(EL2276C) topologies

1 mA supply current (per

amplifier)

70 MHz

3 dB bandwidth

Low cost
Fast disable
Powers down to 0 mA
Single- and dual-supply

operation down to

1 5V

0 15% 0 15 diff gain diff phase

into 150

800V ms slew rate
Large output drive current

100 mA (EL2176C)

55 mA (EL2276C)

Also available without disable in

single (EL2170C) dual
(EL2270C) and quad (EL2470C)

Higher speed EL2180C EL2186C

family also available (3 mA
250 MHz) in single dual and
quad

Applications

Low power battery applications
HDSL amplifiers
Video amplifiers
Cable drivers
RGB amplifiers
Test equipment amplifiers
Current to voltage converters

Ordering Information

Part No

Temp Range

Package

Outline

EL2176CN

40 C to

85 C 8-Pin PDIP

MDP0031

EL2176CS

40 C to

85 C 8-Pin SOIC

MDP0027

EL2276CN

40 C to

85 C 14-Pin PDIP MDP0031

EL2276CS

40 C to

85 C 14-Pin SOIC MDP0027

General Description

The EL2176C EL2276C are single dual current-feedback oper-
ational amplifiers which achieve a

3 dB bandwidth of 70 MHz

at a gain of

1 while consuming only 1 mA of supply current

per amplifier They will operate with dual supplies ranging
from

1 5V to

6V or from single supplies ranging from

12V The EL2176C EL2276C also include a disable power-

down feature which reduces current consumption to 0 mA while
placing the amplifier output in a high impedance state In spite
of its low supply current the EL2276C can output 55 mA while
swinging to

4V on

5V supplies The EL2176C can output

100 mA with similar output swings These attributes make the
EL2176C EL2276C excellent choices for low power and or low
voltage cable-driver HDSL or RGB applications

For Single Dual and Quad applications without disable consid-
er the EL2170C (8-Pin Single)

EL2270C (8-Pin Dual) or

EL2470C (14-Pin Quad) For higher bandwidth applications
where low power is still a concern consider the EL2180C
El2186C family which also comes in similar Single Dual and
Quad configurations The EL2180C EL2186C family provides a

3 dB bandwidth of 250 MHz while consuming 3 mA of supply

current per amplifier

Connection Diagrams

EL2176C SO P-DIP

EL2276C SO P-DIP

2176 1

2176 2

Manufactured under U S Patent No 5 352 989 5 351 012 5 418 495

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

Absolute Maximum Ratings

25 C)

Voltage between V

and V

12 6V

Common-Mode Input Voltage

to V

Differential Input Voltage

Current into

IN or

7 5 mA

Internal Power Dissipation

See Curves

Operating Ambient Temperature Range

40 C to

85 C

Operating Junction Temperature

Plastic Packages

150 C

Output Current (EL2176C)

120 mA

Output Current (EL2276C)

60 mA

Storage Temperature Range

65 C to

150 C

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

100% production tested and QA sample tested per QA test plan QCX0002

100% production tested at T

25 C and QA sample tested at T

25 C

MAX

and T

MIN

per QA test plan QCX0002

III

QA sample tested per QA test plan QCX0002

Parameter is guaranteed (but not tested) by Design and Characterization Data

Parameter is typical value at T

25 C for information purposes only

DC Electrical Characteristics

5V R

150

X ENABLE

0V T

25 C unless otherwise specified

Parameter

Description

Conditions

Min

Typ

Max

Test

Units

Level

Input Offset Voltage

2 5

TCV

Average Input Offset Voltage Drift

Measured from T

MIN

to T

MAX

mV C

Matching

EL2276C only

0 5

Input Current

0 5

Matching

EL2276C only

Input Current

Matching

EL2276C only

1 5

CMRR

Common Mode Rejection Ratio

3 5 V

ICMR

Input Current Common Mode Rejection

3 5V

mA V

PSRR

Power Supply Rejection Ratio

is moved from

4V to

IPSR

Input Current Power Supply Rejection

is moved from

4V to

0 5

mA V

Transimpedance

OUT

2 5V

150

400

Input Resistance

3 5V

Input Capacitance

1 2

CMIR

Common Mode Input Range

3 5

4 0

31in

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

DC Electrical Characteristics

Contd

5V R

150

X ENABLE

0V T

25 C unless otherwise specified

Parameter

Description

Conditions

Min Typ Max

Test

Units

Level

Output Voltage Swing

3 5

4 0

e a

5 Single-Supply High

4 0

e a

5 Single-Supply Low

0 3

Output Current

EL2176C only

100

EL2276C only per Amplifier

Supply Current

ENABLE

2 0V per Amplifier

S(DIS)

Supply Current (Disabled)

ENABLE

4 5V

OUT(DIS)

Output Capacitance (Disabled)

ENABLE

4 5V

4 4

Enable Pin Input Resistance

Measured at ENABLE

2 0V 4 5V

Logic ``1'' Input Current

Measured at ENABLE ENABLE

4 5V

0 04

Logic ``0'' Input Current

Measured at ENABLE ENABLE

DIS

Minimum Voltage at ENABLE to Disable

4 5

Maximum Voltage at ENABLE to Enable

2 0

AC Electrical Characteristics

5V R

1 0 k

X R

150

X ENABLE

0V T

25 C unless otherwise specified

Parameter

Description

Conditions

Min

Typ

Max

Test Level

Units

3 dB BW

3 dB Bandwidth

e a

MHz

3 dB BW

3 dB Bandwidth

e a

MHz

Slew Rate

OUT

2 5V A

e a

400

800

Rise and Fall Time

OUT

500 mV

4 5

Propagation Delay

OUT

500 mV

4 5

Overshoot

OUT

500 mV

3 0

0 1% Settling

OUT

2 5V A

e b

Differential Gain

e a

2 R

150

X (Note 1)

0 15

Differential Phase

e a

2 R

150

X (Note 1)

0 15

Differential Gain

e a

1 R

500

X (Note 1)

0 02

Differential Phase

e a

1 R

500

X (Note 1)

0 01

Turn-On Time

e a

2 V

e a

1V R

150

X (Note 2)

100

OFF

Turn-Off Time

e a

2 V

e a

1V R

150

X (Note 2)

1500

2000

Channel Separation

EL2276C only f

5 MHz

Note 1 DC offset from 0V to 0 714V AC amplitude 286 mV

P-P

3 58 MHz

Note 2 Measured from the application of the logic signal until the output voltage is at the 50% point between initial and final

values

28in

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

Applications Information

Product Description

The EL2176C EL2276C are current-feedback op-
erational amplifiers that offer a wide

3 dB

bandwidth of 70 MHz a low supply current of
1 mA per amplifier and the ability to disable to
0 mA Both products also feature high output
current drive The EL2176C can output 100 mA
while the EL2276C can output 55 mA per ampli-
fier The EL2176C EL2276C work with supply
voltages ranging from a single 3V to

6V and

they are also capable of swinging to with in 1V of
either supply on the input and the output Be-
cause of their current-feedback topology

the

EL2176C EL2276C do not have the normal gain-
bandwidth product associated with voltage-feed-
back operational amplifiers

This allows their

3 dB bandwidth to remain relatively constant

as closed-loop gain is increased This combina-
tion of high bandwidth and low power together
with aggressive pricing make the EL2176C
EL2276C the ideal choice for many low-power
high-bandwidth applications such as portable
computing HDSL and video processing

For Single Dual and Quad applications without
disable

consider the EL2170C (8-Pin Single)

EL2270C (8-Pin Dual) and EL2470C (14-Pin
Quad) If more AC performance is required refer
to the EL2180C EL2186C family which provides
Singles

Duals

and Quads with 250 MHz of

bandwidth while consuming 3 mA of supply cur-
rent per amplifier

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 high-
ly 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 capacitor has been shown

to work well when placed at each supply pin

For good AC performance parasitic capacitance
should be kept to a minimum especially at the
inverting input (see the Capacitance at the In-
verting Input section) Ground plane construc-

tion should be used but it should be removed
from the area near the inverting input to mini-
mize any stray capacitance at that node 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 Sock-
ets add parasitic inductance and capacitance
which will result in some additional peaking and
overshoot

Disable Power-Down

The EL2176C EL2276C amplifiers can be dis-
abled placing their output in a high-impedance
state When disabled each amplifier's supply cur-
rent is reduced to 0 mA

Each EL2176C

EL2276C

amplifier

disabled

when

its

ENABLE pin is floating or pulled up to within
0 5V of the positive supply Similarly each am-
plifier is enabled by pulling its ENABLE pin at
least 3V below the positive supply For

5V sup-

plies this means that an EL2176C EL2276C am-
plifier will be enabled when ENABLE is at 2V or
less and disabled when ENABLE is above 4 5V
Although the logic levels are not standard TTL
this choice of logic voltages allows the EL2176C
EL2276C to be enabled by tying ENABLE to
ground even in

3V single-supply applications

The ENABLE pin can be driven from CMOS
outputs or open-collector TTL

When enabled supply current does vary some-
what with the voltage applied at ENABLE For
example

with

the

supply

voltages

the

EL2176C at

5V if ENABLE is tied to

(rather than ground) the supply current will in-
crease about 15% to 1 15 mA

Capacitance at the Inverting Input

Any manufacturer's high-speed voltage- or cur-
rent-feedback amplifier can be affected by stray
capacitance at the inverting input For inverting
gains this parasitic capacitance has little effect
because the inverting input is a virtual ground
but for non-inverting gains this capacitance (in
conjunction with the feedback and gain resistors)
creates a pole in the feedback path of the amplifi-
er This pole if low enough in frequency has the
same destabilizing effect as a zero in the forward
open-loop response The use of large value feed-

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

Applications Information

Contd

back and gain resistors further exacerbates the
problem by further lowering the pole frequency

The EL2176C EL2276C have been specially de-
signed to reduce power dissipation in the feed-
back network by using large 1 0 k

X feedback and

gain resistors With the high bandwidths of these
amplifiers these large resistor values would nor-
mally cause stability problems when combined
with parasitic capacitance but by internally can-
celing the effects of a nominal amount of parasit-
ic capacitance

the EL2176C EL2276C remain

very stable For less experienced users this fea-
ture makes the EL2176C EL2276C much more
forgiving and therefore easier to use than other
products not incorporating this proprietary cir-
cuitry

The experienced user with a large amount of PC
board layout experience may find in rare cases
that the EL2176C EL2276 C have less band-
width than expected In this case the inverting
input may have less parasitic capacitance than
expected by the internal compensation circuitry
of the EL2176C EL2276C The reduction of feed-
back resistor values (or the addition of a very
small amount of external capacitance at the in-
verting input e g

0 5 pF) will increase band-

width as desired Please see the curves for Fre-
quency Response for Various R

and R

and

Frequency Response for Various C

Feedback Resistor Values

The EL2176C EL2276C have been designed and
specified at gains of

1 and

2 with R

1 0 k

X This value of feedback resistor gives

70 MHz of

3 dB bandwidth at A

1 with

about 1 5 dB of peaking and 60 MHz of

3 dB

bandwidth at A

2 with about 0 5 dB of

peaking Since the EL2176C EL2276C are cur-
rent-feedback amplifiers it is also possible to
change the value of R

to get more bandwidth

As seen in the curve of Frequency Response For
Various R

and R

bandwidth and peaking can

be easily modified by varying the value of the
feedback resistor

Because the EL2176C is a current-feedback am-
plifier the gain-bandwidth product is not a con-
stant for different closed-loop gains This feature

actually allows the EL2176C EL2276C to main-
tain about the same

3 dB bandwidth regard-

less of closed-loop gain However as closed-loop
gain is increased bandwidth decreases slightly
while stability increases

Since the loop stability is improving with higher
closed-loop gains it becomes possible to reduce
the value of R

below the specified 1 0 k

X and

still retain stability resulting in only a slight loss
of bandwidth with increased closed-loop gain

Supply Voltage Range and Single-
Supply Operation

The EL2176C EL2276C have been designed to
operate with supply voltages having a span of
greater than 3V and less than 12V In practical
terms this means that the EL2176C EL2276C
will operate on dual supplies ranging from

1 5V

6V With a single-supply the EL2176C will

operate from

3V to

12V

As supply voltages continue to decrease it be-
comes necessary to provide input and output
voltage ranges that can get as close as possible to
the supply voltages

The EL2176C EL2276C

have an input voltage range that extends to with-
in 1V of either supply So for example on a sin-
gle

5V supply the EL2176C EL2276C have an

input range which spans from 1V to 4V The out-
put range of the EL2176C EL2276C is also quite
large extending to within 1V of the supply rail
On a

5V supply the output is therefore capable

of swinging from

4V to

4V Single-supply

output range is even larger because of the in-
creased negative swing due to the external pull-
down resistor to ground On a single

5V sup-

ply output voltage range is about 0 3V to 4V

Video Performance

For good video performance an amplifier is re-
quired to maintain the same output impedance
and the same frequency response as DC levels are
changed at the output This is especially difficult
when driving a standard video load of 150

X be-

cause of the change in output current with DC
level Until the EL2176C EL2276C good Differ-
ential Gain could only be achieved by running
high idle currents through the output transistors
(to reduce variations in output impedance)
These currents were typically in excess of the

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

Applications Information

Contd

entire 1 mA supply current of each EL2176C
EL2276C amplifier Special circuitry has been in-
corporated in the EL2176C EL2276C to reduce
the variation of output impedance with current
output This results in dG and dP specifications
of 0 15% and 0 15 while driving 150

X at a gain

Video Performance has also been measured with
a 500

X load at a gain of

1 Under these condi-

tions the EL2176C EL2276C have dG and dP
specifications of 0 01% and 0 02

respectively

while driving 500

X at A

Output Drive Capability

In spite of its low 1 mA of supply current the
EL2176C is capable of providing a minimum of

80 mA of output current Similarly each am-

plifier of the EL2276C is capable of providing a
minimum of

50 mA These output drive levels

are unprecedented in amplifiers running at these
supply currents With a minimum

80 mA of

output drive the EL2176C is capable of driving
50

X loads to

4V making it an excellent choice

for driving isolation transformers in telecommu-
nications applications Similarly the

50 mA

minimum output drive of each EL2276C amplifi-
er allows swings of

2 5V into 50

X loads

Driving Cables and Capacitive Loads

When used as a cable driver double termination
is always recommended for reflection-free per-
formance For those applications the back-termi-
nation series resistor will decouple the EL2176C
EL2276C from the cable and allow extensive ca-
pacitive drive However other applications may
have high capacitive loads without a back-termi-
nation resistor In these applications a small se-
ries resistor (usually between 5

X and 50X) can be

placed in series with the output to eliminate most
peaking The gain resistor (R

) can then be cho-

sen to make up for any gain loss which may be
created by this additional resistor at the output
In many cases it is also possible to simply in-
crease the value of the feedback resistor (R

) to

reduce the peaking

Current Limiting

The EL2176C EL2276C have no internal cur-
rent-limiting circuitry If any output is shorted
it is possible to exceed the Absolute Maximum
Ratings for output current or power dissipation
potentially resulting in the destruction of the de-
vice

Power Dissipation

With the high output drive capability of the
EL2176C EL2276C it is possible to exceed the
150 C Absolute Maximum junction temperature
under certain very high load current conditions
Generally speaking when R

falls below about

X it is important to calculate the maximum

junction temperatu re (T

Jmax

) for the application

to determine if power-supply voltages load con-
ditions or package type need to be modified for
the EL2176C EL2276C to remain in the safe op-
erating area These parameters are calculated as
follows

JMAX

MAX

(

MAX

)

where

MAX

Maximum Ambient Temperature

Thermal Resistance of the Package

Number of Amplifiers in the Pack-
age

MAX

Maximum Power Dissipation of
Each Amplifier in the Package

MAX

for each amplifier can be calculated as

follows

MAX

SMAX

)

OUTMAX

)

OUTMAX

))

where

Supply Voltage

SMAX

Maximum Supply Current of 1
Amplifier

OUTMAX

Max Output Voltage of the Ap-
plication

Load Resistance

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

EL2176C EL2276C Macromodel

Revision A March 1995

Transimpedance Stage

AC characteristics used Rf

X RL

150

Connections

input

g1 0 18 17 0 1 0

input

rol 18 0 400K

Vsupply

cdp 18 0 1 9pF

Vsupply

output

Output Stage

subckt EL2176 el

q1 4 18 19 qp

q2 7 18 20 qn

Input Stage

q3 7 19 21 qn

q4 4 20 22 qp

e1 10 0 3 0 1 0

r7 21 6 4

vis 10 9 0V

r8 22 6 4

h2 9 12 vxx 1 0

ios1 7 19 0 4mA

r1 2 11 165

ios2 20 4 0 4mA

l1 11 12 25nH

iinp 3 0 0 5uA

Supply Current

iinm 2 0 4uA

r12 3 0 4Meg

ips 7 4 1nA

Slew Rate Limiting

Error Terms

h1 13 0 vis 600

ivos 0 23 2mA

r2 13 14 1K

vxx 23 0 0V

d1 14 0 dclamp

e4 24 0 3 0 1 0

d2 0 14 dclamp

e5 25 0 7 0 1 0

e6 26 0 4 0

1 0

High Frequency Pole

r9 24 23 0 316K

r10 25 23 3 2K

e2 30 0 14 0 0 00166666666

r11 26 23 3 2K

l3 30 17 0 5uH

c5 17 0 0 69pF

Models

r5 17 0 300

model qn npn(is

5e-15 bf

200 tf

0 01nS)

model qp pnp(is

5e-15 bf

200 tf

0 01nS)

model dclamp d(is

1e-30 ibv

0 266

1 3v n

ends

52in

EL2176CEL2276C

December

1995

Rev

EL2176C EL2276C

70 MHz 1 mA Current Mode Feedback Amp w Disable

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

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

WARNING

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-
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 replace-
ment of defective components and does not cover injury to per-
sons or property or other consequential damages

Printed in U S A

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: EL2276CS

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: EL2276CS