LT1880CS5#TRMPBF - Linear Technology

LT1880

1880fa

TYPICAL APPLICATION

DESCRIPTION

SOT-23, Rail-to-Rail Output,

Picoamp Input Current

Precision Op Amp

The LT

1880 op amp brings high accuracy input perfor-

mance and rail-to-rail output swing to the SOT-23 package.

Input offset voltage is trimmed to less than 150μV and

the low drift maintains this accuracy over the operating

temperature range. Input bias current is an ultralow 900pA

maximum.

The ampliﬁ er works on any total power supply voltage

between 2.7V and 36V (fully speciﬁ ed from 5V to ±15V).

Output voltage swings to within 55mV of the negative

supply and 250mV of the positive supply, which makes

the ampliﬁ er a good choice for low voltage single supply

operation.

Slew rates of 0.4V/μs with a supply current of 1.2mA give

superior response and settling time performance in a low

power precision ampliﬁ er.

The LT1880 is available in a 5-lead SOT-23 package.

Precision Photodiode Ampliﬁ er

FEATURES

APPLICATIONS

n Offset Voltage: 150μV Max

n Input Bias Current: 900pA Max

n Offset Voltage Drift: 1.2μV/°C Max

n Rail-to-Rail Output Swing

n Operates with Single or Split Supplies

n Open-Loop Voltage Gain: 1 Million Min

n 1.2mA Supply Current

n Slew Rate: 0.4V/μs

n Gain Bandwidth: 1.1MHz

n Low Noise: 13nV/√Hz at 1kHz

n Low Proﬁ le (1mm) ThinSOT™ Package

n Thermocouple Ampliﬁ ers

n Bridge Transducer Conditioners

n Instrumentation Ampliﬁ ers

n Battery-Powered Systems

n Photocurrent Ampliﬁ ers L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

–

1880 TA01

39pF

100k, 1%

VS+

VS–

OUT

LT1880

VOUT = 0.1V/μA

320μV OUTPUT OFFSET, WORST CASE OVER 0°C TO 70°C

60kHz BANDWIDTH

5.8μs RISE TIME, 10% TO 90%, 100mV OUTPUT STEP

52μVRMS OUTPUT NOISE, MEASURED ON A 100kHz BW

VS= ±1.5V TO ±18V

S1: SIEMENS INFINEON BPW21 PHOTODIODE (~580pF)

Distribution of Input Offset Voltage

INPUT OFFSET VOLTAGE (μV)

–140

0–20 60

1880 TA01b

–100 –60 20 100 140

PERCENT OF UNITS (%)

LT1880

1880fa

PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS

Supply Voltage (V+ to V–) ......................................... 40V

Differential Input Voltage (Note 2) .......................... ±10V

Input Voltage ......................................................V+ to V–

Input Current (Note 2) ..........................................±10mA

Output Short-Circuit Duration (Note 3) ............ Indeﬁ nite

Operating Temperature Range (Note 4) ...– 40°C to 85°C

Speciﬁ ed Temperature Range (Note 5) ....–40°C to 85°C

Maximum Junction Temperature .......................... 150°C

Storage Temperature Range ..................–65°C to 150°C

Lead Temperature (Soldering, 10 sec)...................300°C

(Note 1)

5 V+

4 –IN

OUT 1

TOP VIEW

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

V– 2

+IN 3

TJMAX = 150°C, θJA = 250°C/W

ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOS Input Offset Voltage

0°C < TA < 70°C

–40°C < TA < 85°C

40 150

200

250

μV

Input Offset Voltage Drift

(Note 6)

0°C < TA < 70°C

–40°C < TA < 85°C

0.3

1.2

μV/°C

IOS Input Offset Current

0°C < TA < 70°C

–40°C < TA < 85°C

150 900

1200

1400

IBInput Bias Current

0°C < TA < 70°C

–40°C < TA < 85°C

150 900

1200

1500

Input Noise Voltage 0.1Hz to 10Hz 0.5 μVp-p

enInput Noise Voltage Density f = 1kHz 13 nV/√Hz

inInput Noise Current Density f = 1kHz 0.07 pA/√Hz

RIN Input Resistance Differential

Common Mode, VCM = 1V to 3.8V

380

210

MΩ

GΩ

CIN Input Capacitance 3.7 pF

VCM Input Voltage Range l(V– + 1.0) (V+ – 1.2) V

The l denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VS = 5V, 0V; VCM = 2.5V unless otherwise noted. (Note 5)

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE

LT1880CS5#PBF LT1880CS5#TRPBF LTUM 5-Lead Plastic TSOT-23 0°C to 70°C

LT1880IS5#PBF LT1880IS5#TRPBF LTVW 5-Lead Plastic TSOT-23 –40°C to 85°C

Consult LTC Marketing for parts speciﬁ ed with wider operating temperature ranges.

Consult LTC Marketing for information on non-standard lead based ﬁ nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁ

cations, go to: http://www.linear.com/tapeandreel/

LT1880

1880fa

ELECTRICAL CHARACTERISTICS

The l denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VS = 5V, 0V; VCM = 2.5V unless otherwise noted. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

CMRR Common Mode Rejection Ratio 1V < VCM < 3.8V l116 135 dB

PSRR Power Supply Rejection Ratio V– = 0V, VCM = 1.5V; 2.7V < V+ < 32V l110 135 dB

Minimum Operating Supply Voltage l2.4 2.7 V

AVOL Large Signal Voltage Gain RL = 10k; 1V < VOUT < 4V

RL = 2k; 1V < VOUT < 4V

RL = 1k; 1V < VOUT < 4V

500

400

300

250

1600

800

400

V/mV

VOL Output Voltage Swing Low No Load

ISINK = 100μA

ISINK = 1mA

130

200

VOH Output Voltage Swing High

(Referred to V+)

V+ = 5V; No Load

V+ = 5V; ISOURCE = 100μA

V+ = 5V; ISOURCE = 1mA

130

150

220

250

270

380

ISSupply Current per Ampliﬁ er V+ = 3V

1.2 1.8

2.2

V+ = 5V

1.2 1.9

2.3

V+ = 12V

1.35 2

2.4

ISC Short-Circuit Current VOUT Short to GND

VOUT Short to V+

GBW Gain-Bandwidth Product f = 20kHz 0.8 1.1 MHz

tSSettling Time 0.01%, VOUT = 1.5V to 3.5V

AV = –1, RL = 2k

10 μs

FPBW Full Power Bandwidth (Note 7) VOUT = 4VP-P 32 kHz

THD Total Harmonic Distortion and Noise VO = 2VP-P, AV = –1, f = 1kHz, Rf = 1k, BW = 22kHz

VO = 2VP-P, AV = 1, f = 1kHz, RL = 10k, BW = 22kHz

0.002

0.0008

SR+Slew Rate Positive AV = –1

0.25

0.2

0.4 V/μs

V/μs

SR–Slew Rate Negative AV = –1

0.25

0.55 V/μs

V/μs

The l denotes the speciﬁ cations which apply over the full operating temperature range, otherwise speciﬁ cations are at TA = 25°C.

VS= ±15V, VCM = 0V unless otherwise noted. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOS Input Offset Voltage

0°C < TA < 70°C

–40°C < TA < 85°C

40 150

200

250

μV

Input Offset Voltage Drift

(Note 6)

0°C < TA < 70°C

–40°C < TA < 85°C

0.3

1.2

μV/°C

IOS Input Offset Current

0°C < TA < 70°C

–40°C < TA < 85°C

150 900

1200

1400

IBInput Bias Current

0°C < TA < 70°C

–40°C < TA < 85°C

150 900

1200

1500

Input Noise Voltage 0.1Hz to 10Hz 0.5 μV/p-p

LT1880

1880fa

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

enInput Noise Voltage Density f = 1kHz 13 nV/√Hz

inInput Noise Current Density f = 1kHz 0.07 pA/√Hz

RIN Input Resistance Differential

Common Mode, VCM = –13.5V to 13.5V

380

190

MΩ

GΩ

CIN Input Capacitance 3.7 pF

VCM Input Voltage Range l–13.5 13.5 V

CMRR Common Mode Rejection Ratio –13.5V < VCM < 13.5V l118 135 dB

+PSRR Positive Power Supply Rejection

Ratio

V– = –15V, VCM = 0V; 1.5V < V+ < 18V l110 135 dB

–PSRR Negative Power Supply Rejection

Ratio

V+ = 15V, VCM = 0V; –1.5V < V– < –18V l110 135 dB

Minimum Operating Supply Voltage l±1.2 ±1.35 V

AVOL Large Signal Voltage Gain RL = 10k; –13.5V < VOUT < 13.5V

RL = 2k; –13.5V < VOUT < 13.5V

1000

700

500

300

1600

1000

V/mV

VOL Output Voltage Swing Low

(Referred to VEE)

No Load

ISINK = 100μA

ISINK = 1mA

130

200

VOH Output Voltage Swing High

(Referred to VCC)

No Load

ISINK = 100μA

ISINK = 1mA

185

195

270

350

370

450

ISSupply Current per Ampliﬁ er

1.5

1.8

2.3

2.8

ISC Short-Circuit Current VOUT Short to V–

VOUT Short to V+

FPBW Full Power Bandwidth (Note 7) VOUT = 14VP-P 9kHz

GBW Gain Bandwidth Product f = 20kHz 0.8 1.1 MHz

THD Total Harmonic Distortion and Noise VO = 25VP-P, AV = –1, f = 100kHz, Rf = 10k, BW = 22kHz

VO = 25VP-P, AV = 1, f = 100kHz, RL = 10k, BW = 22kHz

0.00029

SR+Slew Rate Positive AV = –1

0.25

0.2

0.4 V/μs

V/μs

SR–Slew Rate Negative AV = –1

0.25

0.2

0.55 V/μs

V/μs

ELECTRICAL CHARACTERISTICS

The l denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VS = ± 15V; VCM = 0V unless otherwise noted. (Note 5)

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The inputs are protected by back-to-back diodes. If the differential

input voltage exceeds 10V, see Application Information, the input current

should be limited to less than 10mA.

Note 3: A heat sink may be required to keep the junction temperature

below absolute maximum ratings.

Note 4: The LT1880C and LT1880I are guaranteed functional over the

operating temperature range of –40°C to 85°C.

Note 5: The LT1880C is guaranteed to meet speciﬁ ed performance from

0°C to 70°C and is designed, characterized and expected to meet speciﬁ ed

performance from –40°C to 85°C but is not tested or QA sampled at these

temperatures. The LT1880I is guaranteed to meet speciﬁ ed performance

from –40°C to 85°C.

Note 6: This parameter is not 100% tested.

Note 7: Full power bandwidth is calculated from the slew rate.

FPBW = SR/(2πVP)

LT1880

1880fa

TYPICAL PERFORMANCE CHARACTERISTICS

TEMPERATURE (°C)

–55 –35

INPUT OFFSET VOLTAGE (μV)

125

1880 G01

–15 105

255 856545

200

150

100

–50

–100

–150

–200

TEMPCO: –55°C TO 125°C

10 REPRESENTATIVE UNITS

COMMON MODE VOLTAGE (V)

–15

INPUT BIAS CURRENT (pA)

–10 –5 05

1880 G02

1000

800

600

400

200

–200

–400

–600

–800

–1000 15

IB+

IB–

TA = 25°C

TA = –40°C

TA = 85°C

VS = ±15V

COMMON MODE VOLTAGE (V)

13.0

INPUT BIAS CURRENT (pA)

14.6

1880 G02A

13.4 13.8 14.2

1000

500

–500

–1000

IB–

IB+

TA = –45°C

TA = 25°C

TA = 85°C

VS = ±15V

COMMON MODE VOLTAGE (V)

–13.0

INPUT BIAS CURRENT (pA)

–14.6

1880 G02B

–13.4

–13.8

–14.2

1000

500

–500

–1000

IB–

IB+

TA = –40°C

TA = 25°C

TA = 85°C

VS = ±15V

TEMPERATURE (°C)

–50

INPUT BIAS CURRENT (pA)

–25 025 50

1880 G03

200

150

100

–50

–100

–150

–200

–250

–300 100

IB+

IB–

VS = ±15V

OUTPUT CURRENT (mA)

–10

OUTPUT VOLTAGE

SWING (V–)

OUTPUT VOLTAGE

SWING (V+)

–0.5

–1.0

–1.5

1.5

1.0

0.5

1880 G04

–2 10

–6 2–8 –4 0 4 86

TA = 25°C

TA = 85°C

TA = –40°C

TIME AFTER POWER ON (MIN)

OFFSET VOLTAGE CHANGE (μV)

01234

1880 G05

TA = 25°C

VS = ±15V

VS = ±2.5V

FREQUENCY (Hz)

100

1000

10 100 1k

1880 G08

VS = ±15V

TA = 25°C

CURRENT NOISE

VOLTAGE NOISE

CURRENT NOISE DENSITY (fA/√Hz)

VOLTAGE NOISE DENSITY (nV/√Hz)

TIME (SEC)

NOISE VOLTAGE (0.2μV/DIV)

1880 G09a

24610

VS = ±15V

TA = 25°C

Input Bias Current

vs Common Mode Near VEE Input Bias Current vs Temperature

Output Voltage Swing

vs Load Current

Warm Up Drift en, in vs Frequency 0.1 to 10Hz Noise

Input Offset Voltage

vs Temperature

Input Bias Current

vs Common Mode Voltage

Input Bias Current

vs Common Mode Near VCC

LT1880

1880fa

TYPICAL PERFORMANCE CHARACTERISTICS

TIME (SEC)

NOISE VOLTAGE (0.2μV/DIV)

1880 G09b

20 40 60 100

VS = ±15V

TA = 25°C

FREQUENCY (Hz)

0.1

GAIN (dB)

100k

140

120

100

–20

–40

1880 G10

1 10M

10 100 1k 10k 1M

VS = ±15V

FREQUENCY (Hz)

POWER SUPPLY REJECTION RATIO (dB)

160

140

120

100

1880 G11

0.1 1 10 100 1k 10k 100k 1M

VS = ±15V

–PSRR

+PSRR

FREQUENCY (Hz)

POWER SUPPLY REJECTION RATIO (dB)

160

140

120

100

1880 G12

110 100 1k 10k 100k 1M

VS = ±15V

FREQUENCY (Hz)

10k

VOLTAGE GAIN (dB)

PHASE SHIFT (DEG)

–10

–20

–30

100

–20

–40

–60

–80

–100

100k 1M 10M

1880 G13

VS = ±15V

PHASE SHIFT

GAIN

SETTLING TIME (μs)

OUTPUT STEP (V)

–2

–4

–6

–8

–10 10 20 25

1880 G14

515 30 35 40

0.1%

0.01%

VS = ±15V

AV = –1

SETTLING TIME (μs)

OUTPUT STEP (V)

–2

–4

–6

–8

–10 10 20 25

1880 G15

515 30 35

0.1%

0.01%

VS = ±15V

AV = 1

TEMPERATURE (°C)

–50

GAIN BANDWIDTH

PRODUCT (MHz) SLEW RATE (V/μs)

–25 025 50

1880 G16

0.5

0.4

0.3

1.14

1.12

1.10

100

GBW

VS = ±15V

PHASE MARGIN (DEG)

SLEW RATE

POWER SUPPLY (±V)

GAIN BANDWIDTH

PRODUCT (MHz) SLEW RATE (V/μs)

2.5 57.5 10

1880 G17

12.5

0.5

0.4

0.3

1.12

1.11

1.10

GBW

TA = 25°C

PHASE MARGIN (DEG)

SLEW RATE

CMRR vs Frequency Gain and Phase vs Frequency Settling Time vs Output Step

Settling Time vs Output Step

Slew Rate, Gain-Bandwidth

Product and Phase Margin

vs Temperature

Slew Rate, Gain-Bandwidth

Product and Phase Margin

vs Power Supply

0.01 to 1Hz Noise Gain vs Frequency PSRR vs Frequency

LT1880

1880fa

TYPICAL PERFORMANCE CHARACTERISTICS

FREQUENCY (Hz)

GAIN (dB)

–10

–20

–30

–40 100M10k 100k 10M

1880 G18

1k 1M

1000pF

500pF

0pF

FREQUENCY (Hz)

GAIN (dB)

–10

–20

–30

–40 100M10k 100k 10M

1880 G19

1k 1M

1000pF

0pF

500pF

FREQUENCY (MHz)

OUTPUT IMPEDANCE (Ω)

0.01 1.0 10 100

1880 G17A

0.1

100

1.0

0.1

0.01

VS = ±15V

AV = 100

AV = 1

AV = 10

FREQUENCY (Hz)

THD + NOISE (%)

10 1k 10k 100k

1880 G17B

100

1.0

0.1

0.01

0.001

0.0001

VS = 5V, 0V

VCM = 2.5V

Rf = RG = 1k

VOUT = 2VP-P

RL = 10k

AV = 1

AV = –1

VOUT

(20mV/DIV)

TIME (2μs/DIV) 1880 G20

AV = –1

NO LOAD

VOUT

(20mV/DIV)

TIME (2μs/DIV) 1880 G21

AV = 1

NO LOAD

VOUT

(20mV/DIV)

TIME (2μs/DIV) 1880 G22

AV = 1

CL = 500pF

VOUT

(5V/DIV)

TIME (50μs/DIV) 1880 G23

AV = –1

VOUT

(5V/DIV)

TIME (50μs/DIV) 1880 G24

AV = 1

Total Harmonic Distortion + Noise

vs Frequency Small Signal Response Small Signal Response

Small Signal Response Large Signal Response Large Signal Response

Gain vs Frequency

with CLOAD, AV = –1

Gain vs Frequency

with CLOAD, AV = 1 Output Impedance vs Frequency

LT1880

1880fa

The LT1880 single op amp features exceptional input

precision with rail-to-rail output swing. Slew rate and small

signal bandwidth are superior to other ampliﬁ ers with

comparable input precision. These characteristics make

the LT1880 a convenient choice for precision low voltage

systems and for improved AC performance in higher voltage

precision systems. Obtaining beneﬁ cial advantage of the

precision inherent in the ampliﬁ er depends upon proper

applications circuit design and board layout.

Preserving Input Precision

Preserving the input voltage accuracy of the LT1880

requires that the applications circuit and PC board layout

do not introduce errors comparable to or greater than the

40μV offset. Temperature differentials across the input

connections can generate thermocouple voltages of 10’s

of microvolts. PC board layouts should keep connections

to the ampliﬁ er’s input pins close together and away from

heat dissipating components. Air currents across the board

can also generate temperature differentials.

The extremely low input bias currents, 150pA, allow high

accuracy to be maintained with high impedance sources and

feedback networks. The LT1880’s low input bias currents

are obtained by using a cancellation circuit on-chip. This

causes the resulting IBIAS+ and IBIAS– to be uncorrelated, as

implied by the lOS speciﬁ cation being comparable to IBIAS.

The user should not try to balance the input resistances in

each input lead, as is commonly recommended with most

ampliﬁ ers. The impedance at either input should be kept

as small as possible to minimize total circuit error.

PC board layout is important to insure that leakage currents

do not corrupt the low IBIAS of the ampliﬁ er. In high

precision, high impedance circuits, the input pins should

be surrounded by a guard ring of PC board interconnect,

with the guard driven to the same common mode voltage

as the ampliﬁ er inputs.

Input Common Mode Range

The LT1880 output is able to swing nearly to each power

supply rail, but the input stage is limited to operating

between V– + 1V and V+ – 1.2V. Exceeding this common

mode range will cause the gain to drop to zero, however

no gain reversal will occur.

APPLICATIONS INFORMATION

Input Protection

The inverting and noninverting input pins of the LT1880

have limited on-chip protection. ESD protection is provided

to prevent damage during handling. The input transistors

have voltage clamping and limiting resistors to protect

against input differentials up to 10V. Short transients

above this level will also be tolerated. If the input pins can

see a sustained differential voltage above 10V, external

limiting resistors should be used to prevent damage to

the ampliﬁ er. A 1k resistor in each input lead will provide

protection against a 30V differential voltage.

Capacitive Loads

The LT1880 can drive capacitive loads up to 600pF in unity

gain. The capacitive load driving capability increases as

the ampliﬁ er is used in higher gain conﬁ gurations, see the

graph labled Capacitive Load Response. Capacitive load

driving may be increased by decoupling the capacitance

from the output with a small resistance.

CAPACITIVE LOAD (pF)

OVERSHOOT (%)

010 100 1000 10000

1880 G25

AV = 10

AV = 1

VS = ±15V

TA = 25°C

Getting Rail-to-Rail Operation without Rail-to-Rail

Inputs

The LT1880 does not have rail-to-rail inputs, but for most

inverting applications and noninverting gain applications,

this is largely inconsequential. Figure 1 shows the basic

op amp conﬁgurations, what happens to the op amp

inputs, and whether or not the op amp must have rail-

to-rail inputs.

Capacitance Load Response

LT1880

1880fa

APPLICATIONS INFORMATION

–

VREF

VIN

INVERTING: AV = –RF/RG

OP AMP INPUTS DO NOT MOVE,

BUT ARE FIXED AT DC BIAS

POINT VREF

INPUT DOES NOT HAVE TO BE

RAIL-TO-RAIL

–

VREF

VIN

NONINVERTING: AV = 1 +RF/RG

INPUTS MOVE BY AS MUCH AS

VIN, BUT THE OUTPUT MOVES

INPUT MAY NOT HAVE TO BE

RAIL-TO-RAIL

–

VIN

NONINVERTING: AV = +1

INPUTS MOVE AS MUCH AS

OUTPUT

INPUT MUST BE

RAIL-TO-RAIL FOR OVERALL

CIRCUIT RAIL-TO-RAIL

PERFORMANCE 1880 F01

Figure 1. Some Op Amp Conﬁ gurations Do Not Require

Rail-to Rail Inputs to Achieve Rail-to-Rail Outputs

The circuit of Figure 2 shows an extreme example of the

inverting case. The input voltage at the 1M resistor can

swing ±13.5V and the LT1880 will output an inverted,

divided-by-ten version of the input voltage. The input

accuracy is limited by the resistors to 0.2%. Output

referred, this error becomes 2.7mV. The 40μV input offset

voltage contribution, plus the additional error due to input

bias current times the ~100k effective source impedance,

contribute only negligibly to error.

Precision Photodiode Ampliﬁer

Photodiode ampliﬁers usually employ JFET op amps be-

cause of their low bias current; however, when precision

is required, JFET op amps are generally inadequate due to

their relatively high input offset voltage and drift. The

LT1880 provides a high degree of precision with very low

bias current (IB = 150pA typical) and is therefore appli-

cable to this demanding task. Figure 3 shows an LT1880

conﬁgured as a transimpedance photodiode ampliﬁer.

1.5V

–1.5V

100k, 0.1%

1M, 0.1%

VIN

±1.35V

OUTPUT

SWING

±13.5V SWINGS

WELL OUTSIDE

SUPPLY RAILS

–

LT1880

1880 F02

–

OUT

RF 51.1k

–5V

PHOTODIODE

(SEE TEXT) LT1880

WORST-CASE

OUTPUT OFFSET

≤196μV AT 25°C

≤262μV 0°C TO 70°C

≤323μV –40°C TO 85°C

1880 F02

Figure 2. Extreme Inverting Case: Circuit Operates Properly with

Input Voltage Swing Well Outside Op Amp Supply Rails. Figure 3. Precision Photodiode Ampliﬁ er

LT1880

1880fa

APPLICATIONS INFORMATION

The transimpedance gain is set to 51.1kΩ by RF. The

feedback capacitor, CF, may be as large as desired where

response time is not an issue, or it may be selected for

maximally ﬂat response and highest possible bandwidth

given a photodiode capacitance CD. Figure 4 shows a

chart of CF and rise time versus CD for maximally ﬂat

response. Total output offset is below 262μV, worst-case,

over temperature (0°C to 70°C). With a 5V output swing,

this guarantees a minimum 86dB dynamic range over

temperature (0°C to 70°C), and a full-scale photodiode

current of 98μA.

Single-Supply Current Source for Platinum RTD

The precision, low bias current input stage of the LT1880

makes it ideal for precision integrators and current

sources. Figure 5 shows the LT1880 providing a simple

precision current source for a remote 1kΩ RTD on a 4-wire

connection. The LT1634 reference places 1.25V at the

noninverting input of the LT1880, which then maintains

its inverting input at the same voltage by driving 1mA

of current through the RTD and the total 1.25kΩ of

resistance set by R1 and R2. Imprecise components R4

and C1 ensure circuit stability, which would otherwise be

excessively dependant on the cable characteristics. R5 is

also noncritical and is included to improve ESD immunity

and decouple any cable capacitance from the LT1880’s

output. The 4-wire cable allows Kelvin sensing of the RTD

voltage while excluding the cable IR drops from the voltage

reading. With 1mA excitation, a 1kΩ RTD will have 1V

across it at 0°C, and +3.85mV/°C temperature response.

This voltage can be easily read in myriad ways, with the

best method depending on the temperature region to be

emphasized and the particular ADC that will be reading

the voltage.

0.1 1 10 100 1000

100

0.1

CD (pF)

RISE TIME

RISE TIME (μs), CF (pF)

100mV OUTPUT STEP

1880 F04

–

150k, 1%

LT1634ACS8

-1.25

1.24K

0.1%

10Ω

0.1μF

1kΩ

AT 0°C

RTD*

180Ω, 5%

1k, 5%

VOUT = 1.00V AT 0°C + 3.85mV/°C

–50°C TO 600°C

–

*OMEGA F3141 1kΩ, 0.1% PLATINUM RTD (800) 826-6342

LT1880

1880 F05

Figure 4. Feedback CF and Rise Time vs Photodiode CD

Figure 5. Single Supply Current Source for Platinum RTD

LT1880

1880fa

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

SIMPLIFIED SCHEMATIC

PACKAGE DESCRIPTION

1880 SD

Q59

Q48

Q16

Q58

Q41

Q38

Q44

V+

V–

Q1 Q2 Q45

Q46

Q47

Q12

Q14 Q20

Q24Q23

R3 R4 R27

R38

100μA

35μA

21μA

7μA 10μA

RCM2

RCM1

500Ω

R22

500Ω

CM1

CM2

CM3

+IN

–IN

OUT

CX1

V–

Q7 Q8

1.50 – 1.75

(NOTE 4)

2.80 BSC

0.30 – 0.45 TYP

5 PLCS (NOTE 3)

DATUM ‘A’

0.09 – 0.20

(NOTE 3) S5 TSOT-23 0302 REV B

PIN ONE

2.90 BSC

(NOTE 4)

0.95 BSC

1.90 BSC

0.80 – 0.90

1.00 MAX 0.01 – 0.10

0.20 BSC

0.30 – 0.50 REF

NOTE:

1. DIMENSIONS ARE IN MILLIMETERS

2. DRAWING NOT TO SCALE

3. DIMENSIONS ARE INCLUSIVE OF PLATING

3.85 MAX

0.62

MAX

0.95

REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

1.4 MIN

2.62 REF

1.22 REF

4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

5. MOLD FLASH SHALL NOT EXCEED 0.254mm

6. JEDEC PACKAGE REFERENCE IS MO-193

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

LT1880

1880fa

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 0909 REV A • PRINTED IN USA

RELATED PARTS

TYPICAL APPLICATION

PART NUMBER DESCRIPTION COMMENTS

LT1782 Rugged, General Purpose SOT-23 Op Amp Rail-to-Rail I/O

LT1792 Low Noise JFET Op Amp 4.2nV/√Hz

LT1881/LT1882 Dual/Quad Precision Op Amps 50μV VOS(MAX), 200pA IB(MAX) Rail-to-Rail Output

LTC2050 Zero Drift Op Amp in SOT-23 3μV VOS(MAX), Rail-to-Rail Output

LT6010 135μA Rail-to-Rail Output Precision Op Amp Lower Power Version of LT1880

–

1880 TA02

0.01μF

1.2pF

LT1880

–

LT1806

V+

V–

220k, 5%

10k

100k, 1%

0.01μF

0.1μF

J1: ON SEMI MMBF4416 JFET

N1:ON SEMI MMBT3904 NPN

S1: SIEMENS/INFINEON SFH213FA PHOTODIODE (~3pF)

VSUPPLY = ±5V

BANDWIDTH = 7MHz

NOISE FIGURE = 2dB AT 100kHz, 25°C

AZ = 100kΩ

VOUT

47Ω

TIME DOMAIN

RESPONSE TRIM

47Ω

All SOT-23 JFET Input Transimpedance Photodiode Ampliﬁ er