LINER LT1880 Sot-23, rail-to-rail output, picoamp input current precision op amp Datasheet

LT1880
SOT-23, Rail-to-Rail Output,
Picoamp Input Current
Precision Op Amp
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FEATURES
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DESCRIPTIO
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.
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) ThinSOTTM Package
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.
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APPLICATIO S
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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.
Thermocouple Amplifiers
Bridge Transducer Conditioners
Instrumentation Amplifiers
Battery-Powered Systems
Photocurrent Amplifiers
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.
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TYPICAL APPLICATIO
Precision Photodiode Amplifier
Distribution of Input Offset Voltage
C1
39pF
35
VS+
Vλ
–
LT1880
S1
+
OUT
VOUT = 0.1V/µA
VS
PERCENT OF UNITS (%)
30
R1
100k, 1%
25
20
15
10
5
–
1880 TA01
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)
0
–140 –100
100
60
–60 –20 20
INPUT OFFSET VOLTAGE (µV)
140
1880 TA01b
1
LT1880
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
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
TOP VIEW
V–
LT1880CS5
LT1880IS5
5 V+
OUT 1
2
+IN 3
4 –IN
S5 PART
MARKING
S5 PACKAGE
5-LEAD PLASTIC SOT-23
TJMAX = 150°C, θJA = 250°C/W
LTUM
LTVW
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
VOS
Input Offset Voltage
Input Offset Voltage Drift
(Note 6)
IOS
IB
CONDITIONS
MIN
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
Input Offset Current
Input Bias Current
TYP
MAX
UNITS
40
150
200
250
µV
µV
µV
0.3
0.3
1.2
1.2
µV/°C
µV/°C
150
900
1200
1400
pA
pA
pA
150
900
1200
1500
pA
pA
pA
Input Noise Voltage
0.1Hz to 10Hz
0.5
µVP-P
en
Input Noise Voltage Density
f = 1kHz
13
nV/√Hz
in
Input 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
(V –
pF
(V+ – 1.2)
VCM
Input Voltage Range
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
500
400
400
300
300
250
1600
●
Minimum Operating Supply Voltage
AVOL
Large Signal Voltage Gain
●
●
RL = 1k; 1V < VOUT < 4V
●
2
Output Voltage Swing Low
2.4
●
RL = 10k; 1V < VOUT < 4V
RL = 2k; 1V < VOUT < 4V
VOL
+ 1.0)
No Load
ISINK = 100µA
ISINK = 1mA
●
●
●
2.7
V
V/mV
V/mV
V/mV
V/mV
V/mV
V/mV
800
400
20
35
130
V
55
65
200
mV
mV
mV
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
VOH
Output Voltage Swing High
(Referred to V+)
V+ = 5V; No Load
IS
Supply Current per Amplifier
MIN
●
●
●
V+ = 5V; ISOURCE = 100µA
V+ = 5V; ISOURCE = 1mA
V+ = 3V
TYP
MAX
UNITS
130
150
220
250
270
380
mV
mV
mV
1.2
1.8
2.2
mA
mA
1.2
1.9
2.3
mA
mA
1.35
2
2.4
mA
mA
●
V+ = 5V
●
V+ = 12V
●
ISC
Short-Circuit Current
VOUT Short to GND
VOUT Short to V+
GBW
Gain-Bandwidth Product
f = 20kHz
tS
Settling Time
0.01%, VOUT = 1.5V to 3.5V
AV = –1, RL = 2k
FPBW
Full Power Bandwidth (Note 7)
VOUT = 4VP-P
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
SR+
Slew Rate Positive
AV = –1
SR –
Slew Rate Negative
●
●
10
10
18
20
mA
mA
0.8
1.1
MHz
10
µs
32
kHz
0.002
0.0008
%
%
0.25
0.2
0.4
●
V/µs
V/µs
0.25
0.25
0.55
●
V/µs
V/µs
AV = –1
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
VOS
Input Offset Voltage
Input Offset Voltage Drift
(Note 6)
IOS
IB
CONDITIONS
MIN
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
0°C < TA < 70°C
–40°C < TA < 85°C
●
●
Input Offset Current
Input Bias Current
TYP
MAX
UNITS
40
150
200
250
µV
µV
µV
0.3
0.3
1.2
1.2
µV/°C
µV/°C
150
900
1200
1400
pA
pA
pA
150
900
1200
1500
pA
pA
pA
Input Noise Voltage
0.1Hz to 10Hz
0.5
µVP-P
en
Input Noise Voltage Density
f = 1kHz
13
nV/√Hz
in
Input 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
VCM
Input Voltage Range
CMRR
Common Mode Rejection Ratio
+PSRR
–PSRR
3.7
pF
●
–13.5
–13.5V < VCM < 13.5V
●
118
135
dB
Positive Power Supply Rejection Ratio
V–
●
110
135
dB
Negative Power Supply Rejection Ratio
V+ = 15V, VCM = 0V; –1.5V < V – < –18V
●
110
135
dB
Minimum Operating Supply Voltage
= –15V, VCM
= 0V; 1.5V < V+ < 18V
●
13.5
±1.2
±1.35
V
V
3
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
AVOL
Large Signal Voltage Gain
RL = 10k; –13.5V < VOUT < 13.5V
●
RL = 2k; –13.5V < VOUT < 13.5V
●
MIN
TYP
1000
700
500
300
1600
MAX
UNITS
V/mV
V/mV
V/mV
V/mV
1000
VOL
Output Voltage Swing Low
(Referred to VEE)
No Load
ISINK = 100µA
ISINK = 1mA
●
●
●
25
35
130
65
75
200
mV
mV
mV
VOH
Output Voltage Swing High
(Referred to VCC)
No Load
ISOURCE = 100µA
ISOURCE = 1mA
●
●
●
185
195
270
350
370
450
mV
mV
mV
IS
Supply Current per Amplifier
●
1.5
1.8
2.3
2.8
mA
mA
ISC
Short-Circuit Current
VOUT Short to V –
●
10
10
25
25
mA
mA
●
10
10
20
20
mA
mA
9
kHz
1.1
MHz
VOUT Short to V+
FPBW
Full Power Bandwidth (Note 7)
GBW
Gain Bandwidth Product
f = 20kHz
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
SR+
Slew Rate Positive
AV = –1
SR –
Slew Rate Negative
VOUT = 14VP-P
0.00029
0.00029
%
%
0.25
0.2
0.4
●
V/µs
V/µs
0.25
0.2
0.55
●
V/µs
V/µs
AV = –1
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.
4
0.8
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)
LT1880
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TYPICAL PERFOR A CE CHARACTERISTICS
Input Bias Current vs Common
Mode Voltage
Input Offset Voltage vs
Temperature
TA = 25°C
TA = –40°C
TA = 85°C
800
INPUT BIAS CURRENT (pA)
100
50
0
–50
–100
–150
600
400
IB –
200
0
–200
IB +
–400
–600
5
25
45 65 85 105 125
TEMPERATURE (°C)
VS = ±15V
–1000
–15
–10
0
5
10
–5
COMMON MODE VOLTAGE (V)
1880 G01
IB+
–500
TA = –45°C
TA = 25°C
TA = 85°C
INPUT BIAS CURRENT (pA)
150
IB–
IB+
–1000
–14.6
TA = –40°C
TA = 25°C
TA = 85°C
–13.8
–14.2
–13.4
COMMON MODE VOLTAGE (V)
VS = ±15V
IB –
100
50
0
–100
IB +
–150
–200
–300
–50
–25
25
50
0
TEMPERATURE (°C)
75
CURRENT NOISE DENSITY (fA/√Hz)
VOLTAGE NOISE DENSITY (nV/√Hz)
VS = ±15V
4
3
2
VS = ±2.5V
1
0
1
2
3
4
TIME AFTER POWER ON (MIN)
5
1880 G05
TA = 25°C
–1.5
1.5
TA = 25°C
1.0
TA = 85°C
0.5
TA = –40°C
–10 –8 –6 –4 –2 0 2
4 6
OUTPUT CURRENT (mA)
100
8
10
1880 G04
en, in vs Frequency
1000
5
TA = 85°C
–1.0
1880 G03
Warm Up Drift
TA = 25°C
TA = –40°C
–0.5
–50
1880 G02B
6
14.6
Output Voltage Swing
vs Load Current
–250
–13.0
13.8
14.2
13.4
COMMON MODE VOLTAGE (V)
1880 G02A
OUTPUT VOLTAGE
SWING (V+)
200
500
–500
–1000
13.0
Input Bias Current vs
Temperature
VS = ±15V
0
15
OUTPUT VOLTAGE
SWING (V–)
1000
INPUT BIAS CURRENT (pA)
0
1880 G02
Input Bias Current vs Common
Mode Near VEE
OFFSET VOLTAGE CHANGE (µV)
500
–800
–200
–55 –35 –15
0
VS = ±15V
IB–
0.1 to 10Hz Noise
VS = ±15V
TA = 25°C
NOISE VOLTAGE (0.2µV/DIV)
INPUT OFFSET VOLTAGE (µV)
150
1000
1000
TEMPCO: –55°C TO 125°C
10 REPRESENTATIVE UNITS
INPUT BIAS CURRENT (pA)
200
Input Bias Current vs Common
Mode Near VCC
CURRENT NOISE
100
VOLTAGE NOISE
10
VS = ±15V
TA = 25°C
1
1
10
100
FREQUENCY (Hz)
1k
1880 G08
0
2
6
4
TIME (SEC)
8
10
1880 G09a
5
LT1880
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TYPICAL PERFOR A CE CHARACTERISTICS
PSRR vs Frequency
Gain vs Frequency
140
160
VS = ±15V
POWER SUPPLY REJECTION RATIO (dB)
0.01 to 1Hz Noise
NOISE VOLTAGE (0.2µV/DIV)
120
100
GAIN (dB)
80
60
40
20
0
VS = ±15V
TA = 25°C
60
40
TIME (SEC)
80
0.1
10
1
VOLTAGE GAIN (dB)
100
80
60
40
20
40
PHASE SHIFT
1M
–10
5
20
10
25
15
SETTLING TIME (µs)
30
35
1880 G15
6
4
10
–20
GAIN
0
–40
–10
–60
–20
–80
0.1%
0.01%
2
0
–2
–4
0.01%
0.1%
–8
–100
10M
100k
1M
FREQUENCY (Hz)
VS = ±15V
AV = –1
–6
–10
0
5
10
35
15 20 25 30
SETTLING TIME (µs)
0.5
Slew Rate, Gain-Bandwidth
Product and Phase Margin vs
Power Supply
VS = ±15V
SLEW RATE
0.4
68
0.3
64
ΦM
1.14
60
1.12
1.10
–50
GBW
–25
25
50
0
TEMPERATURE (°C)
75
40
1880 G14
100
1880 G16
SLEW RATE (V/µs)
SLEW RATE (V/µs)
OUTPUT STEP (V)
–8
100k 1M
1880 G13
GAIN BANDWIDTH
PRODUCT (MHz)
0.01%
10 100 1k 10k
FREQUENCY (Hz)
0.5
TA = 25°C
0.4
SLEW RATE
64
0.3
ΦM
60
1.12
56
1.11
GBW
1.10
0
2.5
7.5
10
5
POWER SUPPLY (±V)
12.5
15
1880 G17
PHASE MARGIN (DEG)
–2
0
6
40
0
0
0.1%
60
PHASE MARGIN (DEG)
0.01%
2
–6
8
Slew Rate, Gain-Bandwidth
Product and Phase Margin vs
Temperature
VS = ±15V
AV = 1
–4
80
20
Settling Time vs Output Step
4
10
20
1880 G12
0.1%
100
30
–30
10k
0
100k
1
1880 G11
OUTPUT STEP (V)
50
6
20
Settling Time vs Output Step
VS = ±15V
60
120
8
40
0
0.1
PHASE SHIFT (DEG)
POWER SUPPLY REJECTION RATIO (dB)
VS = ±15V
100
1k
10k
FREQUENCY (Hz)
+PSRR
60
Gain and Phase vs Frequency
70
140
10
–PSRR
80
1880 G10
CMRR vs Frequency
160
10
100
100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
1880 G09b
1
120
–40
100
GAIN BANDWIDTH
PRODUCT (MHz)
20
0
–20
VS = ±15V
140
LT1880
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TYPICAL PERFOR A CE CHARACTERISTICS
Gain vs Frequency
with CLOAD, AV = –1
Gain vs Frequency
with CLOAD, AV = 1
Output Impedance vs Frequency
100
10
0
0
1000pF
–10
500pF
500pF
0pF
GAIN (dB)
GAIN (dB)
1000pF
–20
–10
0pF
–20
VS = ±15V
10
AV = 100
AV = 10
1.0
AV = 1
0.1
–30
–30
–40
OUTPUT IMPEDANCE (Ω)
10
–40
10k
1k
100k
1M
FREQUENCY (Hz)
10M
100M
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
0.01
0.01
0.1
1.0
10
FREQUENCY (MHz)
1880 G19
1880 G18
Total Harmonic Distortion + Noise
vs Frequency
100
1880 G17A
Small Signal Response
Small Signal Response
10
THD + NOISE (%)
VS = 5V, 0V
VCM = 2.5V
R = R = 1k
1.0 V f =G 2V
OUT
P-P
RL = 10k
VOUT
(20mV/DIV)
VOUT
(20mV/DIV)
0.1
0.01
AV = –1
0.001
AV = –1
NO LOAD
AV = 1
0.0001
10
100
1k
10k
FREQUENCY (Hz)
TIME (2µs/DIV)
AV = 1
NO LOAD
1880 G20
TIME (2µs/DIV)
1880 G21
100k
1880 G17B
Small Signal Response
Large Signal Response
Large Signal Response
VOUT
(5V/DIV)
VOUT
(20mV/DIV)
AV = 1
CL = 500pF
TIME (2µs/DIV)
1880 G22
VOUT
(5V/DIV)
AV = –1
TIME (50µs/DIV)
1880 G23
AV = 1
TIME (50µs/DIV)
1880 G24
7
LT1880
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APPLICATIO S I FOR ATIO
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 IBIAS+ and IBIAS– to be
uncorrelated, as implied by the lOS specification being
comparable to IBIAS. The user should not try to balance the
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 IBIAS of the amplifier. 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 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
8
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
30
VS = ±15V
TA = 25°C
25
OVERSHOOT (%)
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.
20
15
AV = 1
10
5
0
AV = 10
10
100
1000
CAPACITIVE LOAD (pF)
10000
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.
LT1880
U
W
U U
APPLICATIO S I FOR ATIO
+
VREF
RG
+
VIN
–
VIN
+
VIN
–
–
RF
RF
RG
VREF
INVERTING: AV = –RF/RG
OP AMP INPUTS DO NOT MOVE,
BUT ARE FIXED AT DC BIAS
POINT VREF
NONINVERTING: AV = 1 + RF/RG
INPUTS MOVE BY AS MUCH AS
VIN, BUT THE OUTPUT MOVES
MORE
INPUT DOES NOT HAVE TO BE
RAIL-TO-RAIL
INPUT MAY NOT HAVE TO BE
RAIL-TO-RAIL
NONINVERTING: AV = +1
INPUTS MOVE AS MUCH AS
OUTPUT
INPUT MUST BE RAIL-TORAIL FOR OVERALL CIRCUIT
RAIL-TO-RAIL PERFORMANCE
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.
1.5V
±13.5V SWINGS
WELL OUTSIDE
SUPPLY RAILS
±1.35V
OUTPUT
SWING
+
LT1880
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.
CF
WORST-CASE
OUTPUT OFFSET
≤196µV AT 25°C
≤262µV 0°C TO 70°C
≤323µV –40°C TO 85°C
RF 51.1k
5V
–
VIN
–
1M, 0.1%
PHOTODIODE
(SEE TEXT)
CD
100k, 0.1%
–1.5V
Figure 2. Extreme Inverting Case: Circuit Operates Properly
with Input Voltage Swing Well Outside Op Amp Supply Rails.
LT1880
+
OUT
–5V
Figure 3. Precision Photodiode Amplifier
9
LT1880
U
W
U U
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
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.
R5
180Ω, 5%
+
RISE TIME (µs), CF (pF)
100
1kΩ
AT 0°C
RTD*
CF
10
VOUT = 1.00V AT 0°C + 3.85mV/°C
– –50°C TO 600°C
R4
1k, 5%
R1
1.24K
0.1%
RISE TIME
1
100mV OUTPUT STEP
0.1
0.1
1
10
CD (pF)
100
R2
10Ω
1%
C1
0.1µF
5V
–
+
LT1880
R3
150k, 1%
1000
LT1634ACS8
5V
-1.25
Figure 4. Feedback CF and Rise Time vs Photodiode CD
*OMEGA F3141 1kΩ, 0.1% PLATINUM RTD
(800) 826-6342
Figure 5. Single Supply Current Source for Platinum RTD
10
LT1880
W
W
SI PLIFIED SCHE ATIC
V+
5
R3
R5
R4
R27
CX1
100µA
Q41
Q23
Q6
Q38
RCM1
Q5
CM1
Q4
Q3
Q47
B
A
Q59
Q58
1 OUT
35µA
Q48
Q12
RCM2
CM2
Q16
V–
R1
500Ω
CM3
Q46
C
B
A
–IN 4
+IN 3
Q14
7µA
R2
500Ω
Q24
Q1
Q2
Q20
R22
500Ω
10µA
Q45
Q44
Q7
Q8
R38
21µA
V– 2
1880 SD
U
PACKAGE DESCRIPTIO
S5 Package
5-Lead Plastic SOT-23
(Reference LTC DWG # 05-08-1633)
(Reference LTC DWG # 05-08-1635)
2.80 – 3.10
(.110 – .118)
(NOTE 3)
A
SOT-23
(Original)
.90 – 1.45
(.035 – .057)
SOT-23
(ThinSOT)
1.00 MAX
(.039 MAX)
A1
.00 – .15
(.00 – .006)
.01 – .10
(.0004 – .004)
A2
.90 – 1.30
(.035 – .051)
.80 – .90
(.031 – .035)
L
.35 – .55
(.014 – .021)
.30 – .50 REF
(.012 – .019 REF)
2.60 – 3.00
(.102 – .118)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
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
1.50 – 1.75
(.059 – .069)
(NOTE 3)
PIN ONE
.95
(.037)
REF
.25 – .50
(.010 – .020)
(5PLCS, NOTE 2)
.20
(.008)
A
DATUM ‘A’
L
.09 – .20
(.004 – .008)
(NOTE 2)
A2
1.90
(.074)
REF
A1
S5 SOT-23 0401
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LT1880
U
TYPICAL APPLICATIO
All SOT-23 JFET Input Transimpedance Photodiode Amplifier
C4
1.2pF
V+
R5
100k, 1%
J1
1k
TIME DOMAIN
RESPONSE TRIM
C5
1.2pF
R2
220k, 5%
C1
0.01µF
+
R7
47Ω
5%
U1
LT1880
R1
220k, 5%
–
R3
10k
5%
C2
0.1µF
S1
N1
R6
47Ω
5%
C3
0.01µF
V–
–
U2
LT1806
VOUT
+
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
1880 TA02
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 VOS(MAX), 200pA IB(MAX) Rail-to-Rail Output
LTC2050
Zero Drift Op Amp in SOT-23
3µV VOS(MAX), Rail-to-Rail Output
12
Linear Technology Corporation
1880f LT/TP 0801 2K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2001