SGS Thomson Microelectronics LF357N, LF356N, LF356D, LF355N, LF157N Datasheet

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SINGLE J-FET OPERATIONAL AMPLIFIERS

.HIGH INPUT IMPEDANCE J-FET INPUT

STAGE

.HIGH SPEEDJ-FET OP-AMPs : up to 20MHz,

50V/µs

.OFFSETVOLTAGEADJUSTMENTDOESNOT

DEGRADEDRIFT ORCOMMON-MODE REJECTIONAS IN MOSTOF MONOLITHIC AMPLIFIERS

.INTERNAL COMPENSATION AND LARGE

DIFFERENTIALINPUTVOLTAGECAPABILITY (UPTO V

TYP ICAL AP P LICATIO NS

)

. PRECISIONHIGHSPEED INTEGRATORS

.FAST D/AANDCONVERTERS

.HIGH IMPEDANCE BUFFERS

.WIDEBAND, LOWNOISE, LOW DRIFT

AMPLIFIERS

.LOGARITHIMICAMPLIFIERS

.PHOTOCELL AMPLIFIERS

.SAMPLEANDHOLD CIRCUITS

LF1 55-LF 255-L F355 LF1 56-LF 256-L F356 LF1 57-LF 257-L F357

WIDE BANDWIDTH

DIP8

(PlasticPackage)

ORDER CODES

Part Number

LF355, LF356, LF357 0 LF255, LF256, LF257 –40 LF155, LF156, LF157 –55

Example : LF355N

SO8

(PlasticMicropackage)

Temperature

Range

C, +70oC ••

C, +105oC ••

C, +125oC ••

Package

DESC RIP TI ON

These circuits are monol i thi cJ-FETinput operational amplifi er sincorporat i ngwell m atch ed,high voltage J-FETonthe s amechi pwithstandardbipolartrans i s tors.

This amplifiers feature low inputbiasand offsetcurrents,low input offsetvolt ageand input offs etvoltage drift,coupledwit hoffsetadjustwhichdoesnotdegrade driftorcommon-moderejection.

Thedevicesarealsodesignedforhighslewrate,wide bandwidth,extrem el yfastsettlingtim e,lowvoltageand currentnois eand a lo w1/f nois elevel.

July1998

PIN C ONNEC TI ONS (top v iew)

1 2 3 4

1 - Offset Null 1 2 - Inverting input 3 - Non-inverting input

4-V

5 - Offset Null 2 6 - Output 7-V 8 - N.C.

8 7 6 5

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LF155 - LF156 - LF157

SCHE MATIC DIAGRAM

ADJUSTMENT

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

Supply Voltage ±22 V

Input Voltage - (note 1) ±20 V

Differential Input Voltage ±40 V

Power Dissipation 570 mW

tot

Output Short-circuit Duration Infinite Operating Free Air Temperature Range LF155-LF156-LF157

oper

LF255-LF256-LF257 LF355-LF356-LF357

Storage Temperature Range –65 to 150

stg

-55 to +125

–40 to +105

0to70

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LF155 - LF156 - LF157

ELECTRICAL CHARACTERISTICS

LF155, LF156, LF157 -55 LF255, LF256, LF257 -40

C ≤ T

≤ +125oC ±5V ≤ VCC≤ ±20V

amb

≤ +105oC ±5V ≤ VCC≤ ±20V

amb

(unless otherwise specified)

LF155 - LF156 - LF157

Symbol Parameter

Input Offset Voltage (RS=50Ω)

Input Offset Current - (note 3)

Input Bias Current - (note 3)

Large Signal Voltage Gain (RL=2kΩ,VO=±10V, VCC= ±15V)

T T

amb min.

=25oC

≤ T

amb

=25oC

≤ T

amb

=25oC

≤ T

amb

=25oC

≤ T

amb

≤ T

max.

LF155, LF156, LF157 LF255, LF256, LF257

SVR Supply Voltage Rejection Ratio - (note 4) 85 100 dB

Supply Current (VCC= ±15V, no load)

=25oC LF155, LF255

amb

LF156, LF256 LF157, LF257

Input Offset Voltage Drift (RS=50Ω)5µV/oC

Change in Average Temperature Coefficient with Vioadjust

io/Vio

icm

=50Ω) - (note 2)

Input Common Mode Voltage Range (VCC= ±15V, T

=25oC) ±11 +15.1

amb

CMR Common Mode Rejection Ratio 85 100 dB

±V

GBP Gain Bandwidth Product (V

Output Voltage Swing (VCC= ±15V)

OPP

= 10kΩ =2kΩ

= ±15V, T

=25oC)

amb

LF155, LF255 LF156, LF256 LF157, LF257

SR Slew Rate (V

= 1 LF155, LF255

= 5 LF157, LF257

Input Resistance (T

Input Capacitance (VCC= ±15V, T

Equivalent Input Noise Voltage

= ±15V, T

f = 1000Hz LF155, LF255

= ±15V, T

amb

=25oC, RS= 100Ω)

amb

=25oC)

amb

LF156, LF256

=25oC) 10

=25oC) 3 pF

amb

LF156, LF256 LF157, LF257

f = 100Hz LF155, LF255

LF156, LF256 LF157, LF257

Equivalent Input Noise Current

= ±15V, T

=25oC, f = 100Hz or f = 1000Hz)

amb

Settling Time (VCC= ±15V, T

=25oC) - (note 5)

amb

LF155, LF255 LF156, LF256 LF157, LF257

LF255 - LF256 - LF257

Min. Typ. Max.

6.2

320

20 100

200

2 5 5

4 7 7

0.5 µV/

-12

±12 ±10

±13 ±12

2.5 5

7.5 30

12 50

20 12 12 25 15 15

0.01

1.5

Unit

pA nA nA

V/mV

MHz

V/µs

Ω

√Hz

µs

3/14

LF155 - LF156 - LF157

ELECTRICAL CHARACTERISTICS

LF355, LF356, LF357 0

Symbol Parameter

Input Offset Voltage (RS=50Ω)

Input Offset Current - (note 3)

Input Bias Current - (note 3)

Large Signal Voltage Gain (RL=2kΩ,VO=±10V)

T T

amb min.

=25oC

≤ T

amb

=25oC

≤ T

amb

=25oC

≤ T

amb

=25oC

≤ T

amb

≤ T

max.

C ≤ T

≤ +70oCV

amb

= ±15V

, (unless otherwise specified)

LF355 - LF356 - LF357

Min. Typ. Max.

310

350

20 200

200

2pAnA

SVR Supply Voltage Rejection Ratio - (note 4) 80 100 dB

Supply Current (no load)

Input Offset Voltage Drift (RS=50Ω) - (note 2) 5 µV/oC

Change in Average Temperature Coefficient with Vioadjust

io/Vio

(R Input Common Mode Voltage Range (T

icm

=25oC LF355

amb

=50Ω)

LF356, LF357

=25oC) ±10 +15.1

amb

2 5

0.5 µV/

-12

CMR Common Mode Rejection Ratio 80 100 dB

±V

Output Voltage Swing RL= 10kΩ

OPP

GBP Gain Bandwidth Product T

=25oC) LF355

amb

=2kΩ

LF356

±12 ±10

LF357

SR Slew Rate (T

= 1 LF355

= 5 LF357

Input Resistance (T

Input Capacitance (Tamb = 25oC) 3 pF

Equivalent Input Noise Voltage (T

f = 1000Hz LF355

amb

=25oC)

LF356

=25oC) 10

amb

=25oC, RS= 100Ω)

amb

LF356, LF357

f = 100Hz LF355

LF356, LF357

Equivalent Input Noise Current

Notes: 1. Unless otherwise specified the absolute maximumnegative inputvoltage is equaltothe negative power supply voltage.

2. The temperaturecoefficient of the adjustedinput offset voltage changes only a small amount(0.5µV/

3. The input bias currents are junctionleakage currents which approximately double for every 10

4. Supply voltage rejection is measured for both supply magnitudesincreasing or decreasing simultaneously, inaccordance with

5. Settling time is defined here,fora unitygain inverter connection using 2kΩ resistorsfor the LF155, LF156 series. It is the time

=25oC, f = 100Hz or f = 1000Hz)

amb

Settling Time (T

of adjustment fromits original unadjusted value. Common-mode rejection and open loop voltagegainare alsounaffected by offsetadjustment.

temperature T In anormaloperation the junction temperature rises above the ambienttemperature as a result of internal powerdissipation, P

tot-Tamb=Tamb+Rth(j-a)xPtot

f input currents areto bekept to aminimum. common practise. required for the errorvoltage (the voltage atthe invertinginput pinon theamplifier) to settleto within0.01%ofits final value from

the time a 10V step inputis applied to theinverter. For the LF157 seriesA and the outputstep is 10V.

amb

=25oC) - (note 5) LF355

amb

. Dueto limited production test time, the input bias currentmeasured is correlatedto junction temperature.

where Rt

is the thermal resistance from junction to ambient. Use ofa heatsink is recommended

h(j-a)

LF356, LF357

= -5, thefeedback resistor from output to inputis 2kΩ

±13 ±12

2.5 5

12 50

20 12 25 15

0.01 4

1.5

C typically) for each mV

C increase in thejunction

Unit

pA nA

V/mV

per mV

MHz

V/µs

Ω

√Hz

µs

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APPL ICATION HINTS

The LF155, LF156,LF157seri esareopamps withJFETinputtrans i sto r s .TheseJF E Tshavelargereverse breakdownvoltagesfr om gat etosourceor drain elim i natingtheneedofclampsacrossthe inputs.Therefore large differ enti alinput voltagescan easily be accommodatedwithoutalargeincreaseofinputcur re nt s.The maximumdifferentialinput voltage is independentof thesupplyvoltage.However,neitherofthenegativ einput vol tages s houl dbe allowedto exceedthenegative supplyas this will caus elarge curre ntsto flow which canresultin adestroyedunit.Exceedi ngthe negat i v e common-modelim i toneitherinp utw i l lcauseareversal of thephasetotheoutputandforcethe ampli fi eroutput to the correspondi nghi gh or lowstate . Exceedingthe negativecommon-mo delimit on bothinputs will force theamplifieroutputtoahighstate.Inneithercasedoes a latch occur since raising the input back within the common-moderangeagain putstheinput stageand thustheamplifi erin anormaloperatingmode.Exceedingthepositi vecom mon-modelim i tonasingleinputwil l not ch angethephaseoftheoutputhowever ,ifbothinputsexceedthelimi t, theoutputof theamplifier will be forcedtoahighstate.Theseampli fi erswilloperat ewith the common-m odeinputvoltageequal tothe positi v e supply. In fact, the common-modevol tagec anex ceedthepositiv esupplybyapproximately100mVindependentof supply volt-age and over thefull operatingtemperatur erange.The positive suplly can thereforebeusedasa referenceonaninputas,forexam ple, in asupplycurr entmonitorand/orlimiter .Prec auti ons shouldbetakentoensurethatthepowersupplyforthe integratedcircuitneverbecomesre-versedin polarity orthattheunitisnot inadvertentlyin- st al l edbackwar ds

LF155 - LF156 - LF157

in a socket as an unilim i tedcurrentsurge throu ghthe resul ti ngforwarddiodewithi ntheIC coul dcausefusi ngoftheinternalconductors andresul tinadestroy eduni t.

Becausethese amplifi ersareJFETratherthan MOS FET inputop ampstheydo not requirespecialhandling.

AllofthebiascurrentsintheseamplifiersaresetbyFET currentsources. The draincurrentsforthe amplifiers are therefore essenti al l y independentof supply volt ages.

Aswithmostam pl i f i er s ,careshouldbetakenwithlead dress,c om ponentsplacemen tandsupplydecoupling inordertoensurestability.Forexample,resi storsfrom theoutputtoan inputshouldbe placedwith thebody closetothei nputtominim iz”pickup”andmaximiz ethe frequencyof the feedbackpole bymini mizing the capacitancefromthe input to ground.

A feedbackpole is creat edw henthe feedbackaround any amplifier is resistive. The parallel resistance and capacitanc efromtheinput of thedevice(usual l ythe inverting input)toacgrounds etthefrequenc y ofthepole.In many instanc es the frequency of this pole is muc h greaterthantheexpected3dBfrequencyof the closed loopgainandconsequentlythereisnegligi bleeffect on stability margin. However, if the feedback pole is less than approximately six time the expected3 dB frequencyaleadcapaci t orshouldbeplacedfromtheoutputtothe inputoftheop amp.Thevalueof that added capacitorshouldbesuchthatthe RC tim econs tantof thiscapacitorand theresistanceitparallelsisgreater than or equal to theoriginal feedbackpoletime constant.

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