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LT1880 SOT-23, Rail-to-Rail Output, Picoamp Input Current Precision Op Amp
FEATURES
s s s s s s s s s s s
DESCRIPTIO
Offset Voltage: 150V Max Input Bias Current: 900pA Max Offset Voltage Drift: 1.2V/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/s Gain Bandwidth: 1.1MHz Low Noise: 13nV/Hz at 1kHz Low Profile (1mm) ThinSOTTM Package
The LT(R)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 150V 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/s 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.
APPLICATIO S
s s s s s
Thermocouple Amplifiers Bridge Transducer Conditioners Instrumentation Amplifiers Battery-Powered Systems Photocurrent Amplifiers
TYPICAL APPLICATIO
C1 39pF
Precision Photodiode Amplifier
35 30
Distribution of Input Offset Voltage
PERCENT OF UNITS (%)
R1 100k, 1% VS+ V S1
25 20 15 10 5
-
LT1880 OUT
+
VS
-
VOUT = 0.1V/A
1880 TA01
320V OUTPUT OFFSET, WORST CASE OVER 0C TO 70C 60kHz BANDWIDTH 5.8s RISE TIME, 10% TO 90%, 100mV OUTPUT STEP 52VRMS OUTPUT NOISE, MEASURED ON A 100kHz BW VS = 1.5V TO 18V S1: SIEMENS INFINEON BPW21 PHOTODIODE (~580pF)
0 -140 -100
U
100 60 -60 -20 20 INPUT OFFSET VOLTAGE (V) 140
1880 TA01b
U
U
1
LT1880
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW OUT 1 V- 2 4 -IN 5 V+
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) .. - 40C to 85C Specified Temperature Range (Note 5) ... - 40C to 85C Maximum Junction Temperature .......................... 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
LT1880CS5 LT1880IS5 S5 PART MARKING LTUM LTVW
+IN 3
S5 PACKAGE 5-LEAD PLASTIC SOT-23
TJMAX = 150C, JA = 250C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 5V, 0V; VCM = 2.5V unless otherwise noted. (Note 5)
SYMBOL VOS PARAMETER Input Offset Voltage 0C < TA < 70C -40C < TA < 85C Input Offset Voltage Drift (Note 6) IOS Input Offset Current 0C < TA < 70C -40C < TA < 85C IB Input Bias Current 0C < TA < 70C -40C < TA < 85C Input Noise Voltage en in RIN CIN VCM CMRR PSRR AVOL Input Noise Voltage Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Minimum Operating Supply Voltage Large Signal Voltage Gain RL = 10k; 1V < VOUT < 4V
q q q q q q q q q q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP 40
MAX 150 200 250 1.2 1.2 900 1200 1400 900 1200 1500
UNITS V V V V/C V/C pA pA pA pA pA pA VP-P nV/Hz pA/Hz M G pF
0C < TA < 70C -40C < TA < 85C
0.3 0.3 150
150
0.1Hz to 10Hz f = 1kHz f = 1kHz Differential Common Mode, VCM = 1V to 3.8V (V - + 1.0)
0.5 13 0.07 380 210 3.7 (V+ - 1.2) 135 135 2.4 500 400 400 300 300 250 1600 800 400 20 35 130 55 65 200 2.7
1V < VCM < 3.8V V - = 0V, VCM = 1.5V; 2.7V < V+ < 32V
q q q
116 110
RL = 2k; 1V < VOUT < 4V
q
RL = 1k; 1V < VOUT < 4V
q
V/mV V/mV V/mV V/mV V/mV V/mV mV mV mV
VOL
Output Voltage Swing Low
No Load ISINK = 100A ISINK = 1mA
q q q
2
U
V dB dB V
W
U
U
WW
W
LT1880
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 5V, 0V; VCM = 2.5V unless otherwise noted. (Note 5)
SYMBOL VOH PARAMETER Output Voltage Swing High (Referred to V+) Supply Current per Amplifier CONDITIONS V+ = 5V; No Load V+ = 5V; ISOURCE = 100A V+ = 5V; ISOURCE = 1mA V+ = 3V
q q q q
ELECTRICAL CHARACTERISTICS
MIN
TYP 130 150 220 1.2 1.2
MAX 250 270 380 1.8 2.2 1.9 2.3 2 2.4
UNITS mV mV mV mA mA mA mA mA mA mA mA MHz s kHz % % V/s V/s V/s V/s
IS
V+ = 5V
q
V+ = 12V
q
1.35
q q
ISC GBW tS FPBW THD SR+ SR -
Short-Circuit Current Gain-Bandwidth Product Settling Time Full Power Bandwidth (Note 7) Total Harmonic Distortion and Noise Slew Rate Positive Slew Rate Negative
VOUT Short to GND VOUT Short to V+ f = 20kHz 0.01%, VOUT = 1.5V to 3.5V AV = -1, RL = 2k VOUT = 4VP-P VO = 2VP-P, AV = -1, f = 1kHz, Rf = 1k, BW = 22kHz VO = 2VP-P, AV = 1, f = 1kHz, RL = 10k, BW = 22kHz AV = -1
10 10 0.8
18 20 1.1 10 32 0.002 0.0008
q
0.25 0.2 0.25 0.25
0.4 0.55
AV = -1
q
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS= 15V, VCM = 0V unless otherwise noted. (Note 5)
SYMBOL VOS PARAMETER Input Offset Voltage 0C < TA < 70C -40C < TA < 85C Input Offset Voltage Drift (Note 6) IOS Input Offset Current 0C < TA < 70C -40C < TA < 85C IB Input Bias Current 0C < TA < 70C -40C < TA < 85C Input Noise Voltage en in RIN CIN VCM CMRR +PSRR -PSRR Input Noise Voltage Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range Common Mode Rejection Ratio Positive Power Supply Rejection Ratio Negative Power Supply Rejection Ratio Minimum Operating Supply Voltage -13.5V < VCM < 13.5V V- = -15V, VCM = 0V; 1.5V < V+ < 18V V+ = 15V, VCM = 0V; -1.5V < V - < -18V
q q q q q q q q q q q q q
CONDITIONS
MIN
TYP 40
MAX 150 200 250 1.2 1.2 900 1200 1400 900 1200 1500
UNITS V V V V/C V/C pA pA pA pA pA pA VP-P nV/Hz pA/Hz M G pF
0C < TA < 70C -40C < TA < 85C
0.3 0.3 150
150
0.1Hz to 10Hz f = 1kHz f = 1kHz Differential Common Mode, VCM = -13.5V to 13.5V -13.5 118 110 110
0.5 13 0.07 380 190 3.7 13.5 135 135 135 1.2 1.35
V dB dB dB V
3
LT1880
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 15V; VCM = 0V unless otherwise noted. (Note 5)
SYMBOL AVOL PARAMETER Large Signal Voltage Gain CONDITIONS RL = 10k; -13.5V < VOUT < 13.5V
q
ELECTRICAL CHARACTERISTICS
MIN 1000 700 500 300
TYP 1600 1000 25 35 130 185 195 270 1.5 1.8
MAX
UNITS V/mV V/mV V/mV V/mV
RL = 2k; -13.5V < VOUT < 13.5V
q
VOL
Output Voltage Swing Low (Referred to VEE) Output Voltage Swing High (Referred to VCC) Supply Current per Amplifier
No Load ISINK = 100A ISINK = 1mA No Load ISOURCE = 100A ISOURCE = 1mA
q q q q q q q
65 75 200 350 370 450 2.3 2.8
mV mV mV mV mV mV mA mA mA mA mA mA kHz MHz % % V/s V/s V/s V/s
VOH
IS ISC
Short-Circuit Current
VOUT Short to V -
q
10 10 10 10 0.8
25 25 20 20 9 1.1 0.00029 0.00029
VOUT Short to V+
q
FPBW GBW THD SR+ SR -
Full Power Bandwidth (Note 7) Gain Bandwidth Product Total Harmonic Distortion and Noise Slew Rate Positive Slew Rate Negative
VOUT = 14VP-P f = 20kHz VO = 25VP-P, AV = -1, f = 100kHz, Rf = 10k, BW = 22kHz VO = 25VP-P, AV = 1, f = 100kHz, RL = 10k, BW = 22kHz AV = -1
q
0.25 0.2 0.25 0.2
0.4 0.55
AV = -1
q
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 -40C to 85C.
Note 5: The LT1880C is guaranteed to meet specified performance from 0C to 70C and is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LT1880I is guaranteed to meet specified performance from -40C to 85C. Note 6: This parameter is not 100% tested. Note 7: Full power bandwidth is calculated from the slew rate. FPBW = SR/(2VP)
4
LT1880 TYPICAL PERFOR A CE CHARACTERISTICS
Input Offset Voltage vs Temperature
200 150
INPUT OFFSET VOLTAGE (V)
TEMPCO: -55C TO 125C 10 REPRESENTATIVE UNITS
INPUT BIAS CURRENT (pA)
INPUT BIAS CURRENT (pA)
100 50 0 -50 -100 -150 -200 -55 -35 -15 45 65 85 105 125 TEMPERATURE (C)
1880 G01
5
25
Input Bias Current vs Common Mode Near VEE
1000 VS = 15V 200 150
OUTPUT VOLTAGE SWING (V+)
INPUT BIAS CURRENT (pA)
500
INPUT BIAS CURRENT (pA)
0
IB-
-500
-150 -200 -250 -300 -50 -25
IB +
OUTPUT VOLTAGE SWING (V-)
IB+
-1000 -14.6
-13.8 -14.2 -13.4 COMMON MODE VOLTAGE (V)
Warm Up Drift
6 TA = 25C OFFSET VOLTAGE CHANGE (V) 5 4 3 2 1 0 VS = 2.5V VS = 15V 1000
CURRENT NOISE DENSITY (fA/Hz) VOLTAGE NOISE DENSITY (nV/Hz)
CURRENT NOISE 100
VOLTAGE NOISE 10
NOISE VOLTAGE (0.2V/DIV)
0
1 2 3 4 TIME AFTER POWER ON (MIN)
UW
TA = -40C TA = 25C TA = 85C
Input Bias Current vs Common Mode Voltage
1000 800 600 400 200 0 -200 -400 -600 -800 IB +
TA = 25C TA = -40C TA = 85C
1000
Input Bias Current vs Common Mode Near VCC
IB- VS = 15V
500
IB -
0
IB+
-500 TA = -45C TA = 25C TA = 85C
VS = 15V -1000 -15 -10 0 5 10 -5 COMMON MODE VOLTAGE (V)
15
1880 G02
-1000 13.0
13.8 14.2 13.4 COMMON MODE VOLTAGE (V)
14.6
1880 G02A
Input Bias Current vs Temperature
VS = 15V
Output Voltage Swing vs Load Current
TA = -40C -0.5 -1.0 -1.5 1.5 1.0 0.5 TA = -40C -10 -8 -6 -4 -2 0 2 46 OUTPUT CURRENT (mA) 8 10 TA = 25C TA = 85C TA = 85C TA = 25C
100 50 0 -50 -100
IB -
-13.0
1880 G02B
25 50 0 TEMPERATURE (C)
75
100
1880 G03
1880 G04
en, in vs Frequency
VS = 15V TA = 25C
0.1 to 10Hz Noise
5
1880 G05
1 1 10 100 FREQUENCY (Hz) 1k
1880 G08
VS = 15V TA = 25C 0 2 6 4 TIME (SEC) 8 10
1880 G09a
5
LT1880 TYPICAL PERFOR A CE CHARACTERISTICS
0.01 to 1Hz Noise
140 120
POWER SUPPLY REJECTION RATIO (dB)
NOISE VOLTAGE (0.2V/DIV)
GAIN (dB)
VS = 15V TA = 25C 0 20 60 40 TIME (SEC) 80 100
1880 G09b
CMRR vs Frequency
160
POWER SUPPLY REJECTION RATIO (dB)
VS = 15V
140
VOLTAGE GAIN (dB)
120 100 80 60 40 20 0 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M
30 20 10 0 GAIN
20 0 -20 -40 -60 -80 100k 1M FREQUENCY (Hz)
OUTPUT STEP (V)
Settling Time vs Output Step
8 6 VS = 15V AV = 1 0.1% 0.01%
SLEW RATE (V/s)
VS = 15V SLEW RATE PHASE MARGIN (DEG) 68
SLEW RATE (V/s)
10
OUTPUT STEP (V)
4 2 0
-4 -6 -8 -10 0 5 0.1%
GAIN BANDWIDTH PRODUCT (MHz)
GAIN BANDWIDTH PRODUCT (MHz)
-2 0.01%
20 10 25 15 SETTLING TIME (s)
6
UW
1880 G12
Gain vs Frequency
VS = 15V 160 140 120 100
PSRR vs Frequency
VS = 15V
100 80 60 40 20 0 -20 -40 0.1 1 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
1880 G10
-PSRR 80 60 40 20 0 0.1 1 10 100 1k 10k FREQUENCY (Hz) 100k 1M
1880 G11
+PSRR
Gain and Phase vs Frequency
70 60 50 40 PHASE SHIFT VS = 15V 100 80 60 40
PHASE SHIFT (DEG) 10 8 6 4 2 0 -2 -4 -6 -8 -10
Settling Time vs Output Step
VS = 15V AV = -1 0.1% 0.01%
-10 -20 -30 10k
0.1%
0.01%
-100 10M
1880 G13
0
5
10
15 20 25 30 SETTLING TIME (s)
35
40
1880 G14
Slew Rate, Gain-Bandwidth Product and Phase Margin vs Temperature
0.5 0.5
Slew Rate, Gain-Bandwidth Product and Phase Margin vs Power Supply
TA = 25C
0.4
0.4
SLEW RATE 64
PHASE MARGIN (DEG)
0.3 M 64
0.3
M
60
1.14
1.12 56 1.11 GBW
60 1.12 GBW
30
35
1.10 -50
1.10 0 2.5 7.5 10 5 POWER SUPPLY (V) 12.5 15
-25
25 50 0 TEMPERATURE (C)
75
100
1880 G16
1880 G15
1880 G17
LT1880 TYPICAL PERFOR A CE CHARACTERISTICS
Gain vs Frequency with CLOAD, AV = -1
10 10
1000pF
GAIN (dB)
0pF
GAIN (dB)
-10
500pF
500pF -10 0pF
OUTPUT IMPEDANCE ()
0
-20
-30
-40
1k
10k
100k 1M FREQUENCY (Hz)
10M
Total Harmonic Distortion + Noise vs Frequency
VS = 5V, 0V VCM = 2.5V R = RG = 1k 1.0 V f = 2V OUT P-P RL = 10k 10
THD + NOISE (%)
0.1
0.01 AV = -1 0.001 AV = 1 0.0001 10
100
1k 10k FREQUENCY (Hz)
Small Signal Response
VOUT (20mV/DIV)
AV = 1 CL = 500pF
TIME (2s/DIV)
UW
1880 G18
Gain vs Frequency with CLOAD, AV = 1
100
Output Impedance vs Frequency
VS = 15V
0
1000pF
10 AV = 100 1.0 AV = 1 0.1 AV = 10
-20
-30
-40 100M
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
1880 G19
0.01 0.01
0.1
1.0 10 FREQUENCY (MHz)
100
1880 G17A
Small Signal Response
Small Signal Response
VOUT (20mV/DIV)
VOUT (20mV/DIV)
AV = -1 NO LOAD
100k
1880 G17B
TIME (2s/DIV)
1880 G20
AV = 1 NO LOAD
TIME (2s/DIV)
1880 G21
Large Signal Response
Large Signal Response
VOUT (5V/DIV)
VOUT (5V/DIV)
1880 G22
AV = -1
TIME (50s/DIV)
1880 G23
AV = 1
TIME (50s/DIV)
1880 G24
7
LT1880
APPLICATIO S I FOR ATIO U
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 25 OVERSHOOT (%) 20 15 10 5 0 VS = 15V TA = 25C AV = 1 AV = 10 10 100 1000 CAPACITIVE LOAD (pF) 10000
1880 G25
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 40V 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
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UU
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
APPLICATIO S I FOR ATIO
VREF RG VIN
+ -
RF
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
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 40V input offset voltage contribution, plus the additional error due to input bias current times the ~100k effective source impedance, contribute only negligibly to error.
13.5V SWINGS WELL OUTSIDE SUPPLY RAILS 1.5V 1.35V OUTPUT SWING
+
LT1880 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.
Figure 3. Precision Photodiode Amplifier
+
-
-
U
VIN
W
UU
+ -
RF
VIN
+ -
RG
VREF NONINVERTING: AV = 1 + RF/RG INPUTS MOVE BY AS MUCH AS VIN, BUT THE OUTPUT MOVES MORE 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
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 196V AT 25C 262V 0C TO 70C 323V -40C TO 85C
RF 51.1k 5V
LT1880
OUT
-5V
9
LT1880
APPLICATIO S I FOR ATIO
The transimpedance gain is set to 51.1k 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 262V, worst-case, over temperature (0C-70C). With a 5V output swing, this guarantees a minimum 86dB dynamic range over temperature (0C-70C), and a full-scale photodiode current of 98A. 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 1k RTD on a 4-wire
100
1k AT 0C RTD* R4 1k, 5% C1 0.1F
RISE TIME (s), CF (pF)
10
CF
1
RISE TIME
0.1 0.1 1
100mV OUTPUT STEP 10 CD (pF) 100 1000
R2 10 1%
R3 150k, 1% LT1634ACS8 5V -1.25
Figure 4. Feedback CF and Rise Time vs Photodiode CD
*OMEGA F3141 1k, 0.1% PLATINUM RTD (800) 826-6342
Figure 5. Single Supply Current Source for Platinum RTD
10
+
R1 1.24K 0.1%
-
U
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 1.25k 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 1k RTD will have 1V across it at 0C, 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 180, 5%
W
UU
+
VOUT = 1.00V AT 0C + 3.85mV/C - -50C TO 600C
5V
LT1880
LT1880
SI PLIFIED SCHE ATIC
V+ 5 R3 R4 CX1 100A Q41 Q6 Q38 Q5 Q3 Q4 Q47 B A Q48 Q12 Q16 Q46 C B A 7A Q1 Q2 Q45 Q44 21A V- 2
1880 SD
Q58
R1 500 -IN 4 +IN 3 R2 500
V-
PACKAGE DESCRIPTIO
A A1 A2 L
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)
.20 (.008) DATUM `A' A A2
L
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.
U
W
W
R5
R27
Q23 CM1
Q24
RCM1
35A RCM2 CM2
1 OUT
Q59
CM3 Q14 Q20
10A
R22 500
Q7
Q8
R38
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)
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
2.60 - 3.00 (.102 - .118)
1.50 - 1.75 (.059 - .069) (NOTE 3)
PIN ONE .95 (.037) REF .25 - .50 (.010 - .020) (5PLCS, NOTE 2)
.09 - .20 (.004 - .008) (NOTE 2)
1.90 (.074) REF
A1
S5 SOT-23 0401
11
LT1880
TYPICAL APPLICATIO
All SOT-23 JFET Input Transimpedance Photodiode Amplifier
C4 1.2pF V+ R5 100k, 1% C5 1.2pF
C1 0.01F
R1 220k, 5%
S1
RELATED PARTS
PART NUMBER LT1782 LT1792 LT1881/LT1882 LTC2050 DESCRIPTION Rugged, General Purpose SOT-23 Op Amp Low Noise JFET Op Amp Dual/Quad Precision Op Amps Zero Drift Op Amp in SOT-23 COMMENTS Rail-to-Rail I/O 4.2nV/Hz 50V VOS(MAX), 200pA IB(MAX) Rail-to-Rail Output 3V VOS(MAX), Rail-to-Rail Output
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
1k TIME DOMAIN RESPONSE TRIM J1 R2 220k, 5%
+
U1 LT1880
-
R3 10k 5% C2 0.1F
R7 47 5%
-
U2 LT1806 VOUT
+
N1 C3 0.01F R6 47 5% V-
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, 25C AZ = 100k
1880 TA02
1880f LT/TP 0801 2K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2001

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