Datasheet LT1880 Datasheet (LINEAR TECHNOLOGY)

Download

FEATURES

LT1880

SOT-23, Rail-to-Rail Output,

Picoamp Input Current

Precision Op Amp

DESCRIPTIO

■

Offset Voltage: 150µV Max

■

Input Bias Current: 900pA Max

■

Offset Voltage Drift: 1.2µV/°C Max

■

Rail-to-Rail Output Swing

■

Operates with Single or Split Supplies

■

Open-Loop Voltage Gain: 1 Million Min

■

1.2mA Supply Current

■

Slew Rate: 0.4V/µs

■

Gain Bandwidth: 1.1MHz

■

Low Noise: 13nV/√Hz at 1kHz

■

Low Profile (1mm) ThinSOT

Package

APPLICATIO S

■

Thermocouple Amplifiers

■

Bridge Transducer Conditioners

■

Instrumentation Amplifiers

■

Battery-Powered Systems

■

Photocurrent Amplifiers

TYPICAL APPLICATIO

The LT®1880 op amp brings high accuracy input performance 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 ultra low 900pA maximum.

The amplifier works on any total power supply voltage between 2.7V and 36V (fully specified from 5V to ±15V). Output voltage swings to within 55mV of the negative supply and 250mV of the positive supply, which makes the amplifier 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 amplifier.

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

, LTC and LT are registered trademarks of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

Precision Photodiode Amplifier

39pF

100k, 1%

320µV OUTPUT OFFSET, WORST CASE OVER 0°C TO 70°C 60kHz BANDWIDTH

5.8µs RISE TIME, 10% TO 90%, 100mV OUTPUT STEP 52µV

OUTPUT NOISE, MEASURED ON A 100kHz BW

RMS

= ±1.5V TO ±18V

S1: SIEMENS INFINEON BPW21 PHOTODIODE (~580pF)

–

LT1880

–

OUT

= 0.1V/µA

1880 TA01

Distribution of Input Offset Voltage

PERCENT OF UNITS (%)

0 –140

–100 –60

INPUT OFFSET VOLTAGE (µV)

20 100 140

–20 60

1880 TA01b

LT1880

ABSOLUTE AXI U RATI GS

UUW

PACKAGE/ORDER I FOR ATIO

(Note 1)

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)............ Indefinite

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

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

–

OUT 1

Consult LTC Marketing for parts specified with wider operating temperature ranges.

TOP VIEW

–

+IN 3

S5 PACKAGE

5-LEAD PLASTIC SOT-23

= 150°C, θJA = 250°C/W

JMAX

5 V

4 –IN

ORDER PART

NUMBER

LT1880CS5 LT1880IS5

S5 PART

MARKING

LTUM LTVW

temperature range, otherwise specifications 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 ● 116 135 dB PSRR Power Supply Rejection Ratio V– = 0V, VCM = 1.5V; 2.7V < V+ < 32V ● 110 135 dB

VOL

Input Offset Voltage 40 150 µV

0°C < T

< 70°C ● 200 µV

–40°C < T

Input Offset Voltage Drift 0°C < TA < 70°C ● 0.3 1.2 µV/°C (Note 6) –40°C < T

Input Offset Current 150 900 pA

0°C < T –40°C < T

Input Bias Current 150 900 pA

0°C < T

–40°C < T Input Noise Voltage 0.1Hz to 10Hz 0.5 µV Input Noise Voltage Density f = 1kHz 13 nV/√Hz Input Noise Current Density f = 1kHz 0.07 pA/√Hz Input Resistance Differential 380 MΩ

Common Mode, V Input Capacitance 3.7 pF Input Voltage Range ● (V– + 1.0) (V+ – 1.2) V

Minimum Operating Supply Voltage ● 2.4 2.7 V Large Signal Voltage Gain RL = 10k; 1V < V

Output Voltage Swing Low No Load ● 20 55 mV

SINK

< 85°C ● 250 µV

< 85°C ● 0.3 1.2 µV/°C

< 70°C ● 1200 pA

< 85°C ● 1400 pA

< 70°C ● 1200 pA

< 85°C ● 1500 pA

= 1V to 3.8V 210 GΩ

< 4V 500 1600 V/mV

OUT

= 2k; 1V < V

= 1k; 1V < V

= 100µA ● 35 65 mV = 1mA ● 130 200 mV

< 4V 400 800 V/mV

OUT

< 4V 300 400 V/mV

OUT

● 400 V/mV

● 300 V/mV

● 250 V/mV

P-P

LT1880

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

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

FPBW Full Power Bandwidth (Note 7) V THD Total Harmonic Distortion and Noise VO = 2V

–

Output Voltage Swing High V+ = 5V; No Load ● 130 250 mV (Referred to V

= 5V; I

= 100µA ● 150 270 mV

SOURCE

= 1mA ● 220 380 mV

SOURCE

Supply Current per Amplifier V+ = 3V 1.2 1.8 mA

● 2.2 mA

V+ = 5V 1.2 1.9 mA

● 2.3 mA

V+ = 12V 1.35 2 mA

● 2.4 mA

Short-Circuit Current V

Settling Time 0.01%, V

Short to GND ● 10 18 mA

OUT

Short to V

OUT

= –1, RL = 2k

= 4V

OUT

= 2V

= 1.5V to 3.5V 10 µs

OUT

P-P

, AV = –1, f = 1kHz, Rf = 1k, BW = 22kHz 0.002 %

P-P

, AV = 1, f = 1kHz, RL = 10k, BW = 22kHz 0.0008 %

P-P

● 10 20 mA

32 kHz

Slew Rate Positive AV = –1 0.25 0.4 V/µs

● 0.2 V/µs

Slew Rate Negative AV = –1 0.25 0.55 V/µs

● 0.25 V/µs

The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS= ±15V, VCM = 0V unless otherwise noted. (Note 5)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

CMRR Common Mode Rejection Ratio –13.5V < VCM < 13.5V ● 118 135 dB +PSRR Positive Power Supply Rejection Ratio V– = –15V, VCM = 0V; 1.5V < V+ < 18V ● 110 135 dB –PSRR Negative Power Supply Rejection Ratio V+ = 15V, VCM = 0V; –1.5V < V– < –18V ● 110 135 dB

Input Offset Voltage 40 150 µV

0°C < T

< 70°C ● 200 µV

–40°C < T

< 85°C ● 250 µV

Input Offset Voltage Drift 0°C < TA < 70°C ● 0.3 1.2 µV/°C (Note 6) –40°C < T

< 85°C ● 0.3 1.2 µV/°C

Input Offset Current 150 900 pA

< 70°C ● 1200 pA

0°C < T

–40°C < T

< 85°C ● 1400 pA

Input Bias Current 150 900 pA

< 70°C ● 1200 pA

0°C < T

–40°C < T Input Noise Voltage 0.1Hz to 10Hz 0.5 µV

< 85°C ● 1500 pA

P-P

Input Noise Voltage Density f = 1kHz 13 nV/√Hz Input Noise Current Density f = 1kHz 0.07 pA/√Hz Input Resistance Differential 380 MΩ

Common Mode, V

= –13.5V to 13.5V 190 GΩ

Input Capacitance 3.7 pF Input Voltage Range ● –13.5 13.5 V

Minimum Operating Supply Voltage ● ±1.2 ±1.35 V

LT1880

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOL

FPBW Full Power Bandwidth (Note 7) V GBW Gain Bandwidth Product f = 20kHz 0.8 1.1 MHz THD Total Harmonic Distortion and Noise VO = 25V

–

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.

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.

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

= 2k; –13.5V < V

< 13.5V 1000 1600 V/mV

OUT

< 13.5V 500 1000 V/mV

OUT

● 700 V/mV

● 300 V/mV

Output Voltage Swing Low No Load ● 25 65 mV (Referred to V

= 100µA ● 35 75 mV

SINK

= 1mA ● 130 200 mV

SINK

Output Voltage Swing High No Load ● 185 350 mV (Referred to V

= 100µA ● 195 370 mV

SOURCE

= 1mA ● 270 450 mV

SOURCE

Supply Current per Amplifier 1.5 2.3 mA

● 1.8 2.8 mA

Short-Circuit Current V

OUT

= 25V

Short to V

= 14V

–

P-P

, AV = –1, f = 100kHz, Rf = 10k, BW = 22kHz 0.00029 %

P-P

, AV = 1, f = 100kHz, RL = 10k, BW = 22kHz 0.00029 %

P-P

10 25 mA

● 10 25 mA

10 20 mA

● 10 20 mA

9kHz

Slew Rate Positive AV = –1 0.25 0.4 V/µs

● 0.2 V/µs

Slew Rate Negative AV = –1 0.25 0.55 V/µs

● 0.2 V/µs

Note 5: The LT1880C is guaranteed to meet specified performance from 0°C to 70°C and is designed, characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LT1880I is guaranteed to meet specified 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)

TYPICAL PERFOR A CE CHARACTERISTICS

LT1880

Input Offset Voltage vs Temperature

200

TEMPCO: –55°C TO 125°C 10 REPRESENTATIVE UNITS

150

100

–50

–100

INPUT OFFSET VOLTAGE (µV)

–150

–200

–55 –35

–15 105

255

TEMPERATURE (°C)

Input Bias Current vs Common Mode Near V

1000

500

–500

INPUT BIAS CURRENT (pA)

–1000

–14.6

–

–14.2

COMMON MODE VOLTAGE (V)

–13.8

856545

VS = ±15V

TA = –40°C

= 25°C

= 85°C

–13.4

1880 G01

1880 G02B

125

–13.0

Input Bias Current vs Common Mode Voltage

1000

800 600 400 200

–200 –400

INPUT BIAS CURRENT (pA)

–600 –800

–1000

–15

TA = 25°C T

= –40°C

= 85°C

VS = ±15V

–10

–5

COMMON MODE VOLTAGE (V)

–

Input Bias Current vs Temperature

200

VS = ±15V

150 100

–50 –100 –150

INPUT BIAS CURRENT (pA)

–200 –250 –300

–50

–25

TEMPERATURE (°C)

–

25 50

Input Bias Current vs Common Mode Near V

1000

500

–500

INPUT BIAS CURRENT (pA)

–1000

1880 G02

13.0

–

13.4

COMMON MODE VOLTAGE (V)

13.8

VS = ±15V

TA = –45°C T

14.2

= 25°C = 85°C

14.6

1880 G02A

Output Voltage Swing vs Load Current

TA = 85°C

TA = 25°C

2–8 –4 0 4 86

TA = –40°C

1880 G04

)

–0.5

–1.0

SWING (V

–1.5

OUTPUT VOLTAGE

1.5

1.0

0.5

–10

TA = 25°C

TA = 85°C

TA = –40°C

–6

OUTPUT CURRENT (mA)

–2

)

–

SWING (V

OUTPUT VOLTAGE

100

1880 G03

Warm Up Drift

TA = 25°C

OFFSET VOLTAGE CHANGE (µV)

VS = ±15V

VS = ±2.5V

1234

TIME AFTER POWER ON (MIN)

1880 G05

en, in vs Frequency 0.1 to 10Hz Noise

1000

CURRENT NOISE

100

VOLTAGE NOISE

CURRENT NOISE DENSITY (fA/√Hz)

VOLTAGE NOISE DENSITY (nV/√Hz)

10 100 1k

FREQUENCY (Hz)

VS = ±15V

= 25°C

1880 G08

NOISE VOLTAGE (0.2µV/DIV)

VS = ±15V

= 25°C

TIME (SEC)

1880 G09a

LT1880

TYPICAL PERFOR A CE CHARACTERISTICS

0.01 to 1Hz Noise

NOISE VOLTAGE (0.2µV/DIV)

40 TIME (SEC)

CMRR vs Frequency

160

140

120

100

POWER SUPPLY REJECTION RATIO (dB)

100 1k 10k 100k 1M

FREQUENCY (Hz)

VS = ±15V

= 25°C

1880 G09b

VS = ±15V

1880 G12

100

Gain vs Frequency

140

120

100

GAIN (dB)

–20

–40

0.1

1 10M

100 1k 10k

FREQUENCY (Hz)

Gain and Phase vs Frequency

70 60 50 40 30 20 10

VOLTAGE GAIN (dB)

–10 –20 –30

10k

PHASE SHIFT

GAIN

100k 1M 10M

FREQUENCY (Hz)

VS = ±15V

100k

VS = ±15V

1880 G13

1880 G10

100 80 60 40 20 0 –20 –40 –60 –80 –100

PSRR vs Frequency

160

140

120

100

POWER SUPPLY REJECTION RATIO (dB)

0.1 1

Settling Time vs Output Step

VS = ±15V

= –1

PHASE SHIFT (DEG)

6 4 2 0

–2

OUTPUT STEP (V)

–4 –6 –8

–10

515

0.1%

SETTLING TIME (µs)

VS = ±15V

–PSRR

+PSRR

100 1k 10k 100k 1M

FREQUENCY (Hz)

0.1%

0.01%

1880 G11

1880 G14

Settling Time vs Output Step

VS = ±15V

= 1

6 4 2 0

–2

OUTPUT STEP (V)

–4 –6 –8

–10

0.1%

515

SETTLING TIME (µs)

0.01%

Slew Rate, Gain-Bandwidth Product and Phase Margin vs Temperature

0.5 VS = ±15V

0.4

SLEW RATE (V/µs)

0.3

1.14

1.12

PRODUCT (MHz)

GAIN BANDWIDTH

1.10

1880 G15

–50

GBW

–25

TEMPERATURE (°C)

SLEW RATE

25 50

PHASE MARGIN (DEG)

100

1880 G16

Slew Rate, Gain-Bandwidth Product and Phase Margin vs Power Supply

0.5 TA = 25°C

0.4

0.3

1.12

1.11

PRODUCT (MHz) SLEW RATE (V/µs)

GAIN BANDWIDTH

1.10 0

2.5

GBW

SLEW RATE

POWER SUPPLY (±V)

7.5 10

12.5

1880 G17

PHASE MARGIN (DEG)

TYPICAL PERFOR A CE CHARACTERISTICS

LT1880

Gain vs Frequency with C

–10

GAIN (dB)

–20

–30

–40

1k 1M

, AV = –1

LOAD

FREQUENCY (Hz)

0pF

Total Harmonic Distortion + Noise vs Frequency

VS = 5V, 0V V

= 2.5V

= RG = 1k

1.0

0.1

= 2V

OUT

RL = 10k

P-P

1000pF

500pF

100M10k 100k 10M

1880 G18

Gain vs Frequency with C

–10

GAIN (dB)

–20

–30

–40

LOAD

1k 1M

Small Signal Response

OUT

(20mV/DIV)

, AV = 1

0pF

FREQUENCY (Hz)

1000pF

500pF

1880 G19

Output Impedance vs Frequency

100

VS = ±15V

AV = 100

1.0

0.1

OUTPUT IMPEDANCE (Ω)

100M10k 100k 10M

0.01

0.01 1.0 10 100

AV = 10

AV = 1

0.1 FREQUENCY (MHz)

1880 G17A

Small Signal Response

OUT

(20mV/DIV)

0.01

THD + NOISE (%)

0.001

0.0001 10 1k 10k 100k

AV = –1

AV = 1

100

FREQUENCY (Hz)

Small Signal Response

OUT

(20mV/DIV)

AV = 1

= 500pF

TIME (2µs/DIV)

1880 G17B

1880 G22

AV = –1 NO LOAD

Large Signal Response

OUT

(5V/DIV)

AV = –1

TIME (2µs/DIV)

TIME (50µs/DIV)

1880 G20

1880 G23

AV = 1 NO LOAD

Large Signal Response

OUT

(5V/DIV)

AV = 1

TIME (2µs/DIV)

TIME (50µs/DIV)

1880 G21

1880 G24

LT1880

WUUU

APPLICATIO S I FOR ATIO

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 amplifiers 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 beneficial advantage of the precision inherent in the amplifier 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 amplifier’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 onchip. This causes the resulting I

BIAS

and I

BIAS

–

to be uncorrelated, as implied by the lOS specification being comparable to I

. The user should not try to balance the

BIAS

input resistances in each input lead, as is commonly recommended with most amplifiers. 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 I

of the amplifier. In high

BIAS

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 amplifier 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.

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 amplifier. 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 amplifier is used in higher gain configurations, see the graph labled Capacitive Load Response. Capacitive load driving may be increased by decoupling the capacitance from the output with a small resistance.

Capacitance Load Response

VS = ±15V

= 25°C

OVERSHOOT (%)

10 100 1000 10000

AV = 1

AV = 10

CAPACITIVE LOAD (pF)

1880 G25

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.

WUUU

APPLICATIO S I FOR ATIO

LT1880

REF

INVERTING: AV = –RF/R OP AMP INPUTS DO NOT MOVE, BUT ARE FIXED AT DC BIAS POINT V

INPUT DOES NOT HAVE TO BE RAIL-TO-RAIL

–

REF

–

REF

NONINVERTING: AV = 1 + RF/R INPUTS MOVE BY AS MUCH AS

, BUT THE OUTPUT MOVES

INPUT MAY NOT HAVE TO BE RAIL-TO-RAIL

Figure 1. Some Op Amp Configurations 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.

–

NONINVERTING: AV = +1 INPUTS MOVE AS MUCH AS OUTPUT

INPUT MUST BE RAIL-TORAIL FOR OVERALL CIRCUIT RAIL-TO-RAIL PERFORMANCE

Precision Photodiode Ampliﬁer

Photodiode ampliﬁers usually employ JFET op amps because 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 applicable to this demanding task. Figure 3 shows an LT1880 conﬁgured as a transimpedance photodiode ampliﬁer.

±13.5V SWINGS

WELL OUTSIDE

SUPPLY RAILS

1.5V

±1.35V OUTPUT SWING

LT1880

1M, 0.1%

–

100k, 0.1%

–1.5V

Figure 2. Extreme Inverting Case: Circuit Operates Properly with Input Voltage Swing Well Outside Op Amp Supply Rails.

WORST-CASE OUTPUT OFFSET

≤196µV AT 25°C ≤262µV 0°C TO 70°C ≤323µV –40°C TO 85°C

PHOTODIODE

(SEE TEXT)

RF 51.1k

–

LT1880

–5V

Figure 3. Precision Photodiode Amplifier

OUT

LT1880

WUUU

APPLICATIO S I FOR ATIO

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–70°C). With a 5V output swing, this guarantees a minimum 86dB dynamic range over temperature (0°C–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

100

RISE TIME

100mV OUTPUT STEP

(pF)

RISE TIME (µs), C

0.1

0.1 1 10 100 1000

Figure 4. Feedback CF and Rise Time vs Photodiode C

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.

180Ω, 5%

= 1.00V AT 0°C + 3.85mV/°C

OUT

1kΩ

AT 0°C

RTD*

1k, 5%

1.24K

0.1%

R2 10Ω 1%

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

0.1µF

–

LT1880

150k, 1%

LT1634ACS8

-1.25

–

–50°C TO 600°C

Figure 5. Single Supply Current Source for Platinum RTD

SI PLIFIED SCHE ATIC

LT1880

R3 R4 R27

Q41

Q38

Q59

–

21µA

–IN

+IN

Q58

500Ω

–

Q1 Q2 Q45

PACKAGE DESCRIPTIO

SOT-23

(Original)

.90 – 1.45

(.035 – .057)

.00 – .15

(.00 – .006)

.90 – 1.30

(.035 – .051)

.35 – .55

(.014 – .021)

SOT-23

(ThinSOT)

1.00 MAX

(.039 MAX)

.01 – .10

(.0004 – .004)

.80 – .90

(.031 – .035) .30 – .50 REF

(.012 – .019 REF)

Q46

CX1

C B

Q47

100µA

B A

Q48

Q16

7µA10µA

Q44

S5 Package

5-Lead Plastic SOT-23

(Reference LTC DWG # 05-08-1633) (Reference LTC DWG # 05-08-1635)

2.60 – 3.00

(.102 – .118)

1.50 – 1.75

(.059 – .069)

(NOTE 3)

PIN ONE

CM1

Q12

RCM1

35µA

CM2

RCM2

Q14

R22 500Ω

NOTE:

1. CONTROLLING DIMENSION: MILLIMETERS

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE

4. DIMENSIONS ARE INCLUSIVE OF PLATING

5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

6. MOLD FLASH SHALL NOT EXCEED .254mm

7. PACKAGE EIAJ REFERENCE IS:

SC-74A (EIAJ) FOR ORIGINAL JEDEL MO-193 FOR THIN

2.80 – 3.10

(.110 – .118)

(NOTE 3)

Q24Q23

CM3

Q20

R38

1880 SD

MILLIMETERS

(INCHES)

OUT

.20

(.008)

DATUM ‘A’

.95

(.037)

REF

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 represen-

.09 – .20

(.004 – .008)

(NOTE 2)

1.90

(.074)

REF

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

.25 – .50

(.010 – .020)

(5PLCS, NOTE 2)

S5 SOT-23 0401

LT1880

TYPICAL APPLICATIO

All SOT-23 JFET Input Transimpedance Photodiode Amplifier

1.2pF

100k, 1%

1k TIME DOMAIN RESPONSE TRIM

220k, 5%

0.01µF

220k, 5%

LT1880

–

0.1µF

0.01µF

R7 47Ω

R3 10k 5%

R6 47Ω 5%

–

1.2pF

–

LT1806

J1: ON SEMI MMBF4416 JFET N1:ON SEMI MMBT3904 NPN S1: SIEMENS/INFINEON SFH213FA PHOTODIODE (~3pF)

= ±5V

SUPPLY

BANDWIDTH = 7MHz NOISE FIGURE = 2dB AT 100kHz, 25°C

= 100kΩ

RELATED PARTS

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 V LTC2050 Zero Drift Op Amp in SOT-23 3µV V

OS(MAX)

OUT

, 200pA I

Rail-to-Rail Output

B(MAX)

, Rail-to-Rail Output

1880 TA02

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507

●

www.linear.com

1880f LT/TP 0801 2K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2001

Datasheet LT1880 Datasheet (LINEAR TECHNOLOGY)

Specifications and Main Features

Frequently Asked Questions

User Manual