View LT1679_551758.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

LT1678/LT1679 Dual/Quad Low Noise, Rail-to-Rail, Precision Op Amps
FEATURES

DESCRIPTIO

Rail-to-Rail Input and Output 100% Tested Low Voltage Noise: 3.9nV/Hz Typ at 1kHz 5.5nV/Hz Max at 1kHz Single Supply Operation from 2.7V to 36V Offset Voltage: 100V Max Low Input Bias Current: 20nA Max High AVOL: 3V/V Min, RL = 10k High CMRR: 100dB Min High PSRR: 106dB Min Gain Bandwidth Product: 20MHz Operating Temperature Range: - 40C to 85C Matching Specifications No Phase Inversion 8-Lead SO and 14-Lead SO Packages
The LT (R)1678/LT1679 are dual/quad rail-to-rail op amps offering both low noise and precision: 3.9nV/Hz wideband noise, 1/f corner frequency of 4Hz and 90nV peak-to-peak 0.1Hz to 10Hz noise are combined with outstanding precision: 100V maximum offset voltage, greater than 100dB common mode and power supply rejection and 20MHz gain bandwidth product. The LT1678/LT1679 bring precision as well as low noise to single supply applications as low as 3V. The input range exceeds the power supply by 100mV with no phase inversion while the output can swing to within 170mV of either rail. The LT1678/LT1679 are offered in the SO-8 and SO-14 packages. A full set of matching specifications are also provided, facilitating their use in matching dependent applications such as a two op amp instrumentation amplifier design. The LT1678/LT1679 are specified for supply voltages of 15V, single 5V as well as single 3V. For a single amplifier with similiar performance, see the LT1677 data sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S

Strain Gauge Amplifiers Portable Microphones Battery-Powered Rail-to-Rail Instrumentation Low Noise Signal Processing Microvolt Accuracy Threshold Detection Infrared Detectors
TYPICAL APPLICATIO
3
Instrumentation Amplifier with Shield Driver
+
1/4 LT1679 1
1k RF 3.4k 5
30k
2
-
GUARD
INPUT
+ -
GUARD
+
8 1/4 LT1679
10
RG 100 6 RG 100
+ -
4 1/4 LT1679 11 -15V 7 OUTPUT 30k
-
9
GAIN = 1000
13
VOLTAGE NOISE (50nV/DIV)
15V
-
1/4 LT1679
14
RF 3.4k
16789 TA01
12
+
1k
U
0.1Hz to 10Hz Voltage Noise
VS = 2.5V 0 2 4 6 TIME (sec) 8 10
16789 TA01b
U
U
sn16789 16789fs
1
LT1678/LT1679
ABSOLUTE
(Note 1)
AXI U
RATI GS
Lead Temperature (Soldering, 10 sec.)................. 300C Operating Temperature Range (Note 4) ............................................. - 40C to 85C Specified Temperature Range (Note 5) ............................................. - 40C to 85C
Supply Voltage ...................................................... 18V Input Voltages (Note 2) ............ 0.3V Beyond Either Rail Differential Input Current (Note 2) ..................... 25mA Output Short-Circuit Duration (Note 3) ............ Indefinite Storage Temperature Range ................. - 65C to 150C
PACKAGE/ORDER I FOR ATIO
TOP VIEW OUT A 1 -IN A 2 +IN A 3 V- 4 A B 8V
+
ORDER PART NUMBER
7 OUT B 6 -IN B 5 +IN B
LT1678CS8 LT1678IS8 S8 PART MARKING 1678 1678I
S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 190C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless otherwise noted.
SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS (Note 6) (Note 11) 0C TA 70C - 40C TA 85C VS =5V, VCM = VS + 0.1V VS =5V, VCM = VS - 0.3V, 0C TA 70C VS =5V, VCM = VS - 0.3V, - 40C TA 85C VS =5V, VCM = - 0.1V VS =5V, VCM = 0V, 0C TA 70C VS =5V, VCM = 0V, - 40C TA 85C VOS Temp IB Average Input Offset Drift (Note 10) Input Bias Current (Note 11) 0C TA 70C - 40C TA 85C

ELECTRICAL CHARACTERISTICS
VS = 5V, VCM = VS + 0.1V VS = 5V, VCM = VS - 0.3V, 0C TA 70C VS = 5V, VCM = VS - 0.3V, - 40C TA 85C VS = 5V, VCM = - 0.1V VS = 5V, VCM = 0V, 0C TA 70C VS = 5V, VCM = 0V, - 40C TA 85C

2
U
U
W
WW
U
W
TOP VIEW OUT A 1 -IN A 2 +IN A 3 V+ 4 +IN B 5 -IN B 6 OUT B 7 B C A D 14 OUT D 13 -IN D 12 +IN D 11 V - 10 +IN C 9 8 -IN C OUT C
ORDER PART NUMBER LT1679CS LT1679IS
S PACKAGE 14-LEAD PLASTIC SO TJMAX = 150C, JA = 160C/ W
MIN
TYP 35 55 75 150 180 200 1.5 1.8 2.0 0.40 2 3 7 0.19 0.19 0.25
MAX 100 270 350 550 750 1000 30 45 50 3 20 35 50 0.40 0.60 0.75
UNITS V V V V V V mV mV mV V/C nA nA nA A A A A A A

-5 -8.4 -10
- 0.41 - 0.45 - 0.47
sn16789 16789fs
LT1678/LT1679
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless otherwise noted.
SYMBOL IOS PARAMETER Input Offset Current CONDITIONS (Note 6) (Note 11) 0C TA 70C - 40C TA 85C

ELECTRICAL CHARACTERISTICS
MIN
TYP 4 5 8 6 10 15 0.1 0.1 0.15 90 180 1600 4.4 6.6 19 3.9 5.3 9 1.2 0.3
MAX 25 35 55 30 40 65 1.6 2.0 2.4
UNITS nA nA nA nA nA nA A A A nVP-P nVP-P nVP-P nV/Hz nV/Hz nV/Hz
VS = 5V, VCM = VS + 0.1V VS = 5V, VCM = VS - 0.3V, 0C TA 70C VS = 5V, VCM = VS - 0.3V, - 40C TA 85C VS = 5V, VCM = - 0.1V VS = 5V, VCM = 0V, 0C TA 70C VS = 5V, VCM = 0V, - 40C TA 85C en Input Noise Voltage 0.1Hz to 10Hz (Note 7) VCM = VS VCM = 0V fO = 10Hz VCM = VS, fO = 10Hz VCM = 0V, fO = 10Hz fO = 1kHz VCM = VS, fO = 1kHz VCM = 0V, fO = 1kHz in VCM RIN CIN CMRR PSRR AVOL Input Noise Current Density Input Voltage Range

Input Noise Voltage Density (Note 8)
5.5
nV/Hz nV/Hz nV/Hz pA/Hz pA/Hz
fO = 10Hz fO = 1kHz - 0.1 0
VS + 0.1V VS - 0.3V 2 4.2
V V G pF dB dB dB dB V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V V/V
Input Resistance Input Capacitance Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain
Common Mode VS = 5V, VCM = 1.9V to 3.9V VS = 5V, VCM = 1.9V to 3.9V VS = 2.7V to 36V, VCM = VO = 1.7V VS = 3.1V to 36V, VCM = VO = 1.7V VS = 3V, RL = 10k, VO = 2.5V to 0.7V VS = 3V, RL = 2k, VO = 2.2V to 0.7V 0C TA 70C -40C TA 85C VS = 3V, RL = 600, VO = 2.2V to 0.7V 0C TA 70C -40C TA 85C VS = 5V, RL = 10k, VO = 4.5V to 0.7V OC < TA < 70C -40 < TA < 85C VS = 5V, RL = 2k, VO = 4.2V to 0.7V 0C TA 70C -40C TA 85C VS = 5V, RL = 600, VO = 4.2V to 0.7V 0C TA 70C -40C TA 85C 98 92 100 98 0.6 0.3 0.5 0.4 0.4 0.20 0.15 0.10 1 0.6 0.3 0.7 0.6 0.5 0.6 0.5 0.4

120 120 125 120 3 2 3 0.9 0.8 0.43 0.40 0.35 3.8 2 2 3.5 3.2 3.0 3.0 2.8 2.5 80 125 130 170 200 250
VOL
Output Voltage Swing Low (Note 11)
Above GND ISINK = 0.1mA 0C TA 70C - 40C TA 85C

mV mV mV
sn16789 16789fs
3
LT1678/LT1679
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless otherwise noted.
SYMBOL VOL PARAMETER Output Voltage Swing Low (Note 11) CONDITIONS (Note 6) Above GND ISINK = 2.5mA 0C TA 70C - 40C TA 85C Above GND ISINK = 10mA 0C TA 70C - 40C TA 85C VOH Output Voltage Swing High (Note 11) Below VS ISOURCE = 0.1mA 0C TA 70C - 40C TA 85C Below VS ISOURCE = 2.5mA 0C TA 70C - 40C TA 85C Below VS ISOURCE = 10mA 0C TA 70C - 40C TA 85C ISC Output Short-Circuit Current (Note 3) VS = 3V
ELECTRICAL CHARACTERISTICS
MIN
TYP 170 195 205 370 440 465 75 85 93 110 195 205 170 200 230
MAX 250 320 350 600 720 770 150 200 250 250 350 375 400 500 550
UNITS mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mA mA mA mA V/s V/s V/s MHz MHz s s

15 13 18 14 4 3.5 3 13 12.5
22 19 29 25 6 5.8 5.5 20 19 1.4 2.4 100 1
VS = 5V
SR
Slew Rate (Note 13)
AV = - 1, RL = 10k RL = 10k, 0C TA 70C RL = 10k, - 40C TA 85C fO = 100kHz fO = 100kHz 2V Step 0.1%, AV = +1 2V Step 0.01%, AV = +1 IOUT = 0 AV = 100, f = 10kHz

GBW tS RO IS VOS
Gain Bandwidth Product (Note 11) Settling Time Open-Loop Output Resistance Closed-Loop Output Resistance Supply Current per Amplifier (Note 12)
2 2.5 35 55 75 2 3 7 94 88 96 94 110 110 120 120
3.4 3.8 150 400 525 30 55 75
mA mA V V V nA nA nA dB dB dB dB
Offset Voltage Match (Notes 11, 15) Noninverting Bias Current Match (Notes 11, 15) Common Mode Rejection Match (Notes 11, 14, 15) Power Supply Rejection Match (Notes 11, 14, 15)
0C TA 70C -40C TA 85C 0C TA 70C -40C TA 85C VS = 5V, VCM = 1.9V to 3.9V

IB+
CMRR PSRR
VS = 2.7V to 36V, VCM = VO = 1.7V VS = 3.1V to 36V, VCM = VO = 1.7V
sn16789 16789fs
4
LT1678/LT1679
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 15V, VCM = VO = 0V unless otherwise noted.
SYMBOL VOS PARAMETER Input Offset Voltage 0C TA 70C - 40C TA 85C VOS Temp IB Average Input Offset Drift (Note 10) Input Bias Current 0C TA 70C - 40C TA 85C IOS Input Offset Current 0C TA 70C - 40C TA 85C en Input Noise Voltage 0.1Hz to 10Hz (Note 7) VCM = 15V VCM = -15V fO = 10Hz VCM = 15V, fO = 10Hz VCM = -15V, fO = 10Hz fO = 1kHz VCM = 15V, fO = 1kHz VCM = -15V, fO = 1kHz in VCM RIN CIN CMRR PSRR AVOL Input Noise Current Density Input Voltage Range (Note 16) Input Resistance Input Capacitance Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain VCM = -13.3V to 14V

ELECTRICAL CHARACTERISTICS
CONDITIONS (Note 6)
MIN
TYP 20 30 45 0.40 2 3 7 3 5 8 90 180 1600 4.4 6.6 19 3.9 5.3 9 1.2 0.3
MAX 150 350 420 3 20 35 50 25 35 55
UNITS V V V V/C nA nA nA nA nA nA nVP-P nVP-P nVP-P nV/Hz nV/Hz nV/Hz
Input Noise Voltage Density
5.5
nV/Hz nV/Hz nV/Hz pA/Hz pA/Hz
fO = 10Hz fO = 1kHz
- 13.3 2 4.2 100 96 106 100 3 2 1 0.8 0.5 0.4 130 124 130 125 7 6 4 1.7 1.4 1.1
14
V G pF dB dB dB dB V/V V/V V/V V/V V/V V/V
Common Mode
VS = 1.7V to 18V
RL = 10k, VO = 14V 0C TA 70C -40C TA 85C RL = 2k, VO = 13.5V 0C TA 70C -40C TA 85C

sn16789 16789fs
5
LT1678/LT1679
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 15V, VCM = VO = 0V unless otherwise noted.
SYMBOL VOL PARAMETER Output Voltage Swing Low CONDITIONS (Note 6) Above - VS ISINK = 0.1mA 0C TA 70C - 40C TA 85C Above - VS ISINK = 2.5mA 0C TA 70C - 40C TA 85C Above - VS ISINK = 10mA 0C TA 70C - 40C TA 85C VOH Output Voltage Swing High Below +VS ISOURCE = 0.1mA 0C TA 70C - 40C TA 85C Below +VS ISOURCE = 2.5mA 0C TA 70C - 40C TA 85C Below +VS ISOURCE = 10mA 0C TA 70C - 40C TA 85C ISC SR Output Short-Circuit Current (Note 3)
ELECTRICAL CHARACTERISTICS
MIN
TYP 110 125 130 170 195 205 370 440 450 80 90 100 110 120 120 200 250 250
MAX 200 230 260 280 350 380 600 700 750 150 200 250 200 300 350 450 500 550
UNITS mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mA mA V/s V/s V/s MHz MHz % s s

20 15 4 3.5 3 13 12.5
35 28 6 5.8 5.5 20 19 0.00025 2.7 3.9 100 1
Slew Rate
RL = 10k (Note 9) RL = 10k (Note 9) 0C TA 70C RL = 10k (Note 9) - 40C TA 85C fO = 100kHz fO = 100kHz RL = 2k, AV = 1, fO = 1kHz, VO = 20VP-P 10V Step 0.1%, AV = +1 10V Step 0.01%, AV = +1 IOUT = 0 AV = 100, f = 10kHz

GBW THD tS RO IS
Gain Bandwidth Product Total Harmonic Distortion Settling Time Open-Loop Output Resistance Closed-Loop Output Resistance Supply Current per Amplifier
2.5 3 132 5 30 45 2 3 7 96 92 100 96 120 115 123 120
3.5 4.5 225 525 630 30 55 75
mA mA dB V V V nA nA nA dB dB dB dB
sn16789 16789fs
Channel Separation VOS Offset Voltage Match (Note 15) Noninverting Bias Current Match (Note 15) Common Mode Rejection Match (Notes 14, 15) Power Supply Rejection Match (Notes 14, 15)
f = 10Hz, VO = 10V, RL = 10k 0C TA 70C -40C TA 85C 0C TA 70C -40C TA 85C VCM = -13.3V to 14V VS = 1.7V to 18V

IB+
CMRR PSRR
6
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The inputs are protected by back-to-back diodes. Current limiting resistors are not used in order to achieve low noise. If differential input voltage exceeds 1.4V, the input current should be limited to 25mA. If the common mode range exceeds either rail, the input current should be limited to 10mA. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum. Note 4: The LT1678C/LT1679C and LT1678I/LT1679I are guaranteed functional over the Operating Temperature Range of - 40C to 85C. Note 5: The LT1678C/LT1679C are guaranteed to meet specified performance from 0C to 70C. The LT1678C/LT1679C are designed, characterized and expected to meet specified performance from - 40C to 85C but is not tested or QA sampled at these temperatures. The LT1678I/ LT1679I are guaranteed to meet specified performance from - 40C to 85C. Note 6: Typical parameters are defined as the 60% yield of parameter distributions of individual amplifier; i.e., out of 100 LT1678/LT1679s, typically 60 op amps will be better than the indicated specification. Note 7: See the test circuit and frequency response curve for 0.1Hz to10Hz tester in the Applications Information section. Note 8: Noise is 100% tested at 15V supplies. Note 9: Slew rate is measured in AV = - 1; input signal is 10V, output measured at 5V. Note 10: This parameter is not 100% tested. Note 11: VS = 5V limits are guaranteed by correlation to VS = 3V and VS = 15V tests. Note 12: VS = 3V limits are guaranteed by correlation to VS = 5V and VS = 15V tests. Note 13: Guaranteed by correlation to slew rate at VS = 15V and GBW at VS = 3V and VS = 15V tests. Note 14: CMRR and PSRR are defined as follows: 1. CMRR and PSRR are measured in V/V on the individual amplifiers. 2. The difference is calculated between the matching sides in V/V. 3. The result is converted to dB. Note 15: Matching parameters are the difference between amplifiers A and B on the LT1678 and between amplifiers A and D and B and C in the LT1679. Note 16: Input range guaranteed by the common mode rejection ratio test.
TYPICAL PERFOR A CE CHARACTERISTICS
Voltage Noise vs Frequency
100 VS = 15V TA = 25C
VOLTAGE NOISE (50nV/DIV)
10 VCM = 14.5V VCM = 0V
1 0.1
1
10 100 FREQUENCY (Hz)
1000
16789 G01
0
2
4 6 TIME (sec)
8
10
16789 G02
VOLTAGE NOISE (50nV/DIV)
NOISE VOLTAGE (nV/Hz)
UW
0.1Hz to 10Hz Voltage Noise
VS = 5V, 0V
0.01Hz to 1Hz Voltage Noise
VS = 5V, 0V
0
20
40 60 TIME (sec)
80
100
16789 G03
sn16789 16789fs
7
LT1678/LT1679 TYPICAL PERFOR A CE CHARACTERISTICS
Voltage Noise vs Temperature
6
RMS VOLTAGE NOISE DENSITY (nV/Hz)
VS = 15V VCM = 0V
NOISE VOLTAGE (pA/Hz)
INPUT BIAS CURRENT (nA)
5 10Hz 4 1kHz 3
2
1 -50
-25
50 25 0 75 TEMPERATURE (C)
Input Bias Current vs Temperature
1400 1200
INPUT BIAS CURRENT (nA)
VS = 15V
VCM = -14V CURRENT OUT OF DUT
INPUT BIAS CURRENT (nA)
OFFSET VOLTAGE (mV)
1000 800 600 400 200 0 -50 -25 25 0 50 75 TEMPERATURE (C) 100 125 VCM = 14.7V CURRENT INTO DUT
Warm-Up Drift vs Time
10
CHANGE IN OFFSET VOLTAGE (V)
VS = 15V TA = 25C 8
PERCENT OF UNITS (%)
SO PACKAGE 6
20 15 10 5 0
VOLTAGE OFFSET (V)
4
2
0
0
1
2 TIME (min)
3
8
UW
100
16789 G04 16789 G07
Current Noise vs Frequency
10 VS = 15V TA = 25C 16 14 12 10 8 6 4 2 0 -2 -4 125 0.1 0.01 0.1 1 FREQUENCY (kHz) 10
16789 G05
Input Bias Current vs Temperature
VS = 15V VCM = 0V
VCM = 0V 1
VCM = 14.5V
-6 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
16789 G06
Input Bias Current Over the Common Mode Range
900 700 500 300 100 -100 -300 -500 -700 -900 VCM = -15.2V 0 8 4 -16 -12 -8 -4 12 COMMON MODE INPUT VOLTAGE (V) 16 VCM = 14.1V VCM = -13.5V VCM = 14.5V VS = 15V TA = 25C 5 4 3 2 1 0 -1 -2 -3 -4
Offset Voltage Shift vs Common Mode
500 400 VOS IS REFERRED TO VCM = 0V 300
OFFSET VOLTAGE (V)
200 100 0 -100 -200
INPUT BIAS CURRENT
-5 -1.0
VS = 1.5V TO 15V TA = 25C 5 TYPICAL PARTS 2.0 -0.8 -0.4 V + 0.4 - (V) VCM - V VCM - V+ (V) V- 1.0
16789 G09
-300 -400 -500
16789 G08
Distribution of Input Offset Voltage Drift (SO-8)
30 VS = 5V, 0V TA = -40C TO 85C 25 111 PARTS (2 LOTS) 200
VOS vs Temperature of Representive Units
VS = 5V, 0V VCM = 0V 100
0
-100
-200
4
16789 G10
-3.0
1.0 2.0 3.0 -2.0 -1.0 0 INPUT OFFSET VOLTAGE DRIFT (V/C)
16789 G11
-300 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
16789 G12
sn16789 16789fs
LT1678/LT1679 TYPICAL PERFOR A CE CHARACTERISTICS
Common Mode Range vs Temperature
5 4 3
SUPPLY CURRENT PER AMPLIFIER (mA)
400 300
COMMON MODE REJECTION RATIO (dB)
VS = 2.5V TO 15V
OFFSET VOLTAGE (mV)
2 1 0 -1 -2 -3 -4 -5 -1.0
25C -55C 125C 25C VOS IS REFERRED TO VCM = 0V 125C V- 1.0 2.0 -0.8 -0.4 V - 0.4 VCM - VS+ (V) VCM - VS- (V)
16789 G09
Power Supply Rejection Ratio vs Frequency
160
POWER SUPPLY REJECTION RATIO (dB)
OPEN LOOP VOLTAGE GAIN (V/V)
140 120 100
VS = 15V TA = 25C
RL = 2k 1
NEGATIVE SUPPLY 80 60 POSITIVE SUPPLY 40 20 0 0.001 0.01 0.1 1 10 FREQUENCY (kHz) 100 1000
OVERSHOOT (%)
Phase Margin, Gain Bandwidth Product and Slew Rate vs Temperature
PHASE MARGIN (DEG)
90 80 70 60 50 40 8 +SR -SR 4 -55 -35 -15 GAIN BANDWIDTH PRODUCT PHASE MARGIN
VS = 15V CL = 15pF AV = -1 RF = RG = 1k 30 25 20 15 10
SLEW RATE (V/s)
6
5 25 45 65 85 105 125 TEMPERATURE (C)
16789 G19
UW
-55C 0
16789 G16
Supply Current vs Supply Voltage
500 4.0 3.5 3.0 TA = 125C 2.5 2.0 1.5 1.0 TA = 25C TA = -55C 160 140 120 100 80 60 40 20
Common Mode Rejection Ratio vs Frequency
VS = 15V TA = 25C VCM = 0V
OFFSET VOLTAGE (V)
200 100
-100 -200 -300 -400 -500
0
5 10 15 SUPPLY VOLTAGE (V)
20
16789 G14
0 10k
100k 1M FREQUENCY (Hz)
10M
16789 G15
Voltage Gain vs Supply Voltage
10 RL = 10k 60
% Overshoot vs Capacitive Load
VS = 15V RL = 2k TO 10k 50 AV = 1 TA = 25C
40 30 20 10 0 10 100 CAPACITIVE LOAD (pF) 1000
16789 G18
RISING EDGE
0.1 0
TA = 25C RL TO GND VCM = VO = VS/2 10 20 SUPPLY VOLTAGE (V) 30
16789 G17
FALLING EDGE
Large Signal Transient Response
GAIN BANDWIDTH PRODUCT, fO = 100kHz (MHz)
50mV 10V
Small Signal Transient Response
0V
-10V
-50mV
AVCL = -1 VS = 15V
5s/DIV
16789 G20
AVCL = 1 VS = 15V CL = 15pF
0.5s/DIV
16789 G21
sn16789 16789fs
9
LT1678/LT1679 TYPICAL PERFOR A CE CHARACTERISTICS
Settling Time vs Output Step (Inverting)
6 5 VS = 15V AV = -1 TA = 25C
5k VIN - + VOUT 5k
SETTLING TIME (s)
SETTLING TIME (s)
VOLTAGE GAIN (dB)
4 3 2 1 0.1% OF FULL SCALE 0.01% OF FULL SCALE 0.01% OF FULL SCALE 0.1% OF FULL SCALE
0 -10 -8 -6
-4 -2 0 2 4 OUTPUT STEP (V)
Gain, Phase Shift vs Frequency
50 40 100 VS = 15V VCM = 14.7V 80 CL = 10pF 50 40
VOLTAGE GAIN (dB)
VOLTAGE GAIN (dB)
PHASE 30 20 10 0
TA = -55C TA = 25C 60 40 20 0
OUTPUT VOLTAGE SWING (V)
TA = 125C TA = -55C TA = 125C TA = 25C GAIN
-10
0.1
1 10 FREQUENCY (MHz)
Closed-Loop Output Impedance vs Frequency
TOTAL HARMONIC DISTORTION + NOISE (%)
100 0.1 VS = 15V
OUTPUT IMPEDANCE ()
10
1
TOTAL HARMONIC DISTORTION + NOISE (%)
AV = 100
0.1
AV = 1
0.01
0.001 10 100 10k 1k FREQUENCY (Hz) 100k 1M
16789 G28
10
UW
6 8
16789 G22 16789 G25
Settling Time vs Output Step (Noninverting)
6 VS = 15V AV = 1 5 TA = 25C
VIN - 2k + VOUT RL = 1k 2k
Gain, Phase Shift vs Frequency
50 40 30 20 10 TA = 25C 0 -10 TA = -55C 0.1 1 10 FREQUENCY (MHz) GAIN 0 -20 100
16789 G24
PHASE TA = -55C
100 VS = 15V VCM = 0V CL = 10pF 80 TA = 25C TA = 125C 60 40 20
PHASE SHIFT (DEG)
4 3 2 0.1% OF 1 FULL SCALE 0 -10 -8 -6 0.01% OF FULL SCALE 0.01% OF FULL SCALE
TA = 125C
0.1% OF FULL SCALE
10
-4 -2 0 2 4 OUTPUT STEP (V)
6
8
10
16789 G23
Gain, Phase Shift vs Frequency
100 VS = 15V VCM = -14V 80 CL = 10pF +VS 0 -0.1 -0.2 -0.3 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 1 10 FREQUENCY (MHz) -20 100
16789 G26
Output Voltage Swing vs Load Current
VS = 15V TA = -55C TA = 125C TA = 25C
PHASE SHIFT (DEG)
-20 100
PHASE SHIFT (DEG)
30 20 10 0 PHASE TA = -55C TA = 125C
60 40 20 TA = 25C GAIN TA = -55C 0.1 TA = 25C 0
TA = 125C TA = 25C
TA = -55C 8 10
-10
-VS
0 -10 -8 -6 -4 -2 0 2 4 6 OUTPUT CURRENT (mA)
16789 G27
Total Harmonic Distortion and Noise vs Frequency for Noninverting Gain
ZL = 2k/15pF VS = 15V VO = 20VP-P AV = 1, 10, 100 MEASUREMENT BANDWIDTH 0.01 = 10Hz TO 80kHz AV = 100 0.1
Total Harmonic Distortion and Noise vs Frequency for Noninverting Gain
ZL = 2k/15pF VS = 15V VO = 20VP-P AV = -1, -10, -100 MEASUREMENT BANDWIDTH 0.01 = 10Hz TO 80kHz AV = -100
0.001 AV = 10 AV = 1 0.0001 20 100 1k FREQUENCY (Hz) 10k 50k
16789 G29
0.001
AV = -10 AV = -1
0.0001 20
100
1k FREQUENCY (Hz)
10k
50k
16789 G30
sn16789 16789fs
LT1678/LT1679
APPLICATIO S I FOR ATIO
Rail-to-Rail Operation To take full advantage of an input range that can exceed the supply, the LT1678/LT1679 are designed to eliminate phase reversal. Referring to the photographs shown in Figure 1, the LT1678/LT1679 are operating in the follower mode (AV = +1) at a single 3V supply. The output of the LT1678/LT1679 clips cleanly and recovers with no phase reversal. This has the benefit of preventing lock-up in servo systems and minimizing distortion components.
Input = -0.5V to 3.5V
3
INPUT VOLTAGE (V)
2
1
Noise Testing
0 -0.5 50s/DIV
16789 F01a
LT1678 Output
3
OUTPUT VOLTAGE (V)
2
The 0.1Hz to 10Hz peak-to-peak noise of the LT1678/ LT1679 are measured in the test circuit shown (Figure 3). The frequency response of this noise tester (Figure 4) indicates that the 0.1Hz corner is defined by only one zero. The test time to measure 0.1Hz to 10Hz noise should not exceed ten seconds, as this time limit acts as an additional zero to eliminate noise contributions from the frequency band below 0.1Hz. Measuring the typical 90nV peak-to-peak noise performance of the LT1678/LT1679 requires special test precautions:
1
0 -0.5 50s/DIV
16789 F01b
Figure 1. Voltage Follower with Input Exceeding the Supply Voltage (VS = 3V)
Unity-Gain Buffer Application When RF 100 and the input is driven with a fast, largesignal pulse (>1V), the output waveform will look as shown in the pulsed operation diagram (Figure 2). During the fast feedthrough-like portion of the output, the input protection diodes effectively short the output to the
1. The device should be warmed up for at least five minutes. As the op amp warms up, its offset voltage changes typically 3V due to its chip temperature increasing 10C to 20C from the moment the power supplies are turned on. In the ten-second measurement interval these temperature-induced effects can easily exceed tens of nanovolts. 2. For similar reasons, the device must be well shielded from air currents to eliminate the possibility of thermoelectric effects in excess of a few nanovolts, which would invalidate the measurements.
sn16789 16789fs
-
+
U
input and a current, limited only by the output short-circuit protection, will be drawn by the signal generator. With RF 500, the output is capable of handling the current requirements (IL 20mA at 10V) and the amplifier stays in its active mode and a smooth transition will occur. As with all operational amplifiers when RF > 2k, a pole will be created with RF and the amplifier's input capacitance, creating additional phase shift and reducing the phase margin. A small capacitor (20pF to 50pF) in parallel with RF will eliminate this problem.
RF 6V/s OUTPUT LT1678
16789 F02
W
UU
Figure 2. Pulsed Operation
11
LT1678/LT1679
APPLICATIO S I FOR ATIO
0.1F 100k 10
GAIN (dB)
* LT1678
2k
+
LT1001
4.7F
-
VOLTAGE GAIN = 50,000 *DEVICE UNDER TEST NOTE: ALL CAPACITOR VALUES ARE FOR NONPOLARIZED CAPACITORS ONLY 24.3k 100k 0.1F
Figure 3. 0.1Hz to 10Hz Noise Test Circuit
3. Sudden motion in the vicinity of the device can also "feedthrough" to increase the observed noise. Current noise is measured in the circuit shown in Figure 5 and calculated by the following formula:
2 2 eno - 130nV * 101 in = 1M 101
) ()( ( )( )
100k
1/ 2
Figure 5.
The LT1678/LT1679 achieve their low noise, in part, by operating the input stage at 100A versus the typical 10A of most other op amps. Voltage noise is inversely proportional while current noise is directly proportional to the square root of the input stage current. Therefore, the LT1678/LT1679's current noise will be relatively high. At low frequencies, the low 1/f current noise corner frequency ( 200Hz) minimizes current noise to some extent. In most practical applications, however, current noise will not limit system performance. This is illustrated in the Total Noise vs Source Resistance plot (Figure 6) where:
TOTAL NOISE DENSITY (nV/Hz)
12
+
500k
-
100
500k
LT1678
eno
16789 F05
U
100 90 80 70 60 50 40 30 0.01
16789 F03
W
UU
+
-
4.3k
22F
SCOPE x1 RIN = 1M 110k
2.2F
0.1
1 10 FREQUENCY (Hz)
100
16789 F04
Figure 4. 0.1Hz to 10Hz Peak-to-Peak Noise Tester Frequency Response
Total Noise = [(op amp voltage noise)2 + (resistor noise)2 + (current noise RS)2]1/2 Three regions can be identified as a function of source resistance:
(i) RS 400. Voltage noise dominates (ii) 400 RS 50k at 1kHz Resistor Noise 400 RS 8k at 10Hz Dominates (iii) RS > 50k at 1kHz Current Noise RS > 8k at 10Hz Dominates
Clearly the LT1678/LT1679 should not be used in region (iii), where total system noise is at least six times higher than the voltage noise of the op amp, i.e., the low voltage noise specification is completely wasted. In this region the LT1113 or LT1169 are better choices.
1000
R R SOURCE RESISTANCE = 2R
VS = 15V TA = 25C
100
AT 1kHz AT 10Hz 10 RESISTOR NOISE ONLY 1 0.1 1 10 SOURCE RESISTANCE (k) 100
16789 F06
Figure 6. Total Noise vs Source Resistance
sn16789 16789fs
LT1678/LT1679
APPLICATIO S I FOR ATIO
Rail-to-Rail Input
The input common mode range for the LT1678/LT1679 can exceed the supplies by at least 100mV. As the common mode voltage approaches the positive rail (+VS - 0.7V), the tail current for the input pair (Q1, Q2) is reduced, which prevents the input pair from saturating (refer to the Simplified Schematic). The voltage drop across the load resistors RC1, RC2 is reduced to less than 200mV, degrading the slew rate, bandwidth, voltage noise, offset voltage and input bias current (the cancellation is shut off). When the input common mode range goes below 1.5V above the negative rail, the NPN input pair (Q1, Q2) shuts off and the PNP input pair (Q8, Q9) turns on. The offset voltage, input bias current, voltage noise and bandwidth are also degraded. The graph of Offset Voltage Shift vs Common Mode shows where the knees occur by displaying the change in offset voltage. The change-over points are temperature dependent; see the graph Common Mode Range vs Temperature.
RL = 600 RL = 1k INPUT VOLTAGE (50V/DIV) RL = 10k TA = 25C VS = 15V RL CONNECTED TO 0V MEASURED ON TEKTRONIX 577 CURVE TRACER -15 -10 -5 0 5 10 15 OUTPUT VOLTAGE (V)
16789 F07
Figure 7. Voltage Gain Split Supply
U
Rail-to-Rail Output The rail-to-rail output swing is achieved by using transistor collectors (Q28, Q29 referring to the Simplified Schematic) instead of customary class A-B emitter followers for the output stage. The output NPN transistor (Q29) sinks the current necessary to move the output in the negative direction. The change in Q29's base emitter voltage is reflected directly to the gain node (collectors of Q20 and Q16). For large sinking currents, the delta VBE of Q29 can dominate the gain. Figure 7 shows the change in input voltage for a change in output voltage for different load resistors connected between the supplies. The gain is much higher for output voltages above ground (Q28 sources current) since the change in base emitter voltage of Q28 is attenuated by the gain in the PNP portion of the output stage. Therefore, for positive output swings (output sourcing current) there is hardly any change in input voltage for any load resistance. Highest gain and best linearity are achieved when the output is sourcing current, which is the case in single supply operation when the load is ground referenced. Figure 8 shows gains for both sinking and sourcing load currents for a worst-case load of 600.
VOLTAGE GAIN SINGLE SUPPLY VS = 5V RL = 600 MEASURED ON TEKTRONIX 577 CURVE TRACER RL TO 0V INPUT VOLTAGE (10V/DIV) RL TO 5V 0 1 2 3 OUTPUT VOLTAGE (V) 4 5
16789 F08
W
UU
Figure 8. Voltage Gain Single Supply
sn16789 16789fs
13
LT1678/LT1679
W
Q35
SI PLIFIED SCHE ATIC
Q17 Q18 R2 50 100A
R1 500
C1 40pF
+
Q4 Q7 R19 2k R20 2k Q20 Q10 Q6 Q11 C2 80pF
+
OUT
Q12
Q5
Q27 C3 40pF Q23 R3 100
D4 D1 Q3 D2 100A
D3
160A
Q31
+
-IN Q19
Q1A Q1B Q2A Q2B
IA R9 200 50A Q9 IC ID
IB Q22 50A Q15 Q14 Q16 Q25
Q30 Q26
R54 100 Q29 R23A 10k R30 2k R26 Q38 100 R23B 10k R15 1k R14 1k R16 1k R25 1k R29 10
R8 200
Q13 x2
Q21
Q24
Q8
R13 100
R21 100
R24 100
IA, IB = 0A VCM > 1.5V ABOVE -VS IC = 200A VCM < 0.7V BELOW +VS ID = 100A VCM < 0.7V BELOW +VS 200A VCM < 1.5V ABOVE -VS 50A VCM > 0.7V BELOW +VS 0A VCM > 0.7V BELOW +VS
16789 SS
+
+IN
C4 20pF
-VS
W
+
14
+VS R32 1.5k R34 2k Q34 Q28 RC1 6k 200A Q32 C10 81pF RC2 6k
sn16789 16789fs
LT1678/LT1679
PACKAGE DESCRIPTIO
.050 BSC
8
.245 MIN
.030 .005 TYP
RECOMMENDED SOLDER PAD LAYOUT .010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP
NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
.050 BSC N 14 13
.245 MIN
1 .030 .005 TYP
2
3
RECOMMENDED SOLDER PAD LAYOUT 1 .010 - .020 x 45 (0.254 - 0.508) 2 3 4 5 6 7
.008 - .010 (0.203 - 0.254)
.016 - .050 (0.406 - 1.270)
NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
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
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 - .197 (4.801 - 5.004) NOTE 3 7 6 5
.045 .005
.160 .005 .228 - .244 (5.791 - 6.197)
.150 - .157 (3.810 - 3.988) NOTE 3
1
2
3
4
.053 - .069 (1.346 - 1.752)
.004 - .010 (0.101 - 0.254)
.016 - .050 (0.406 - 1.270)
.014 - .019 (0.355 - 0.483) TYP
.050 (1.270) BSC
SO8 0303
S Package 14-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.337 - .344 (8.560 - 8.738) NOTE 3 12 11 10 9 8
.045 .005
N .160 .005 .228 - .244 (5.791 - 6.197) N/2 N/2 .150 - .157 (3.810 - 3.988) NOTE 3
.053 - .069 (1.346 - 1.752)
0 - 8 TYP
.004 - .010 (0.101 - 0.254)
.014 - .019 (0.355 - 0.483) TYP
.050 (1.270) BSC
S14 0502
sn16789 16789fs
15
LT1678/LT1679
TYPICAL APPLICATIO
Bridge Reversal Eliminates 1/f Noise and Offset Drift of a Low Noise, Non-autozeroed, Bipolar Amplifier. Circuit Gives 14nV Noise Level or 19 Effective Bits Over a 10mV Span
VREF 3 4 5,6,7,8 2 5V 1
1
350
350
350
350
100 0.1%
VREF 100k 3 4 5,6,7,8 1
2
2X SILICONIX Si9801 2
RELATED PARTS
PART NUMBER LT1028/LT1128 LT1115 LT1124/LT1125 LT1126/LT1127 LT1226 LT1498/LT1499 LT1677 LT1792 LT1793 LT1806 LT1881/LT1882 LT1884/LT1885 DESCRIPTION Ultralow Noise Precision Op Amps Ultralow Noise, Low distortion Audio Op Amp Dual/Quad Low Noise, High Speed Precision Op Amps Dual/Quad Decompensated Low Noise, High Speed Precision Op Amps Low Noise, Very High Speed Op Amp 10MHz, 5V/s, Dual/Quad Rail-to-Rail Input and Output Op Amps Single Version of LT1678/LT1679 Low Noise, Precision JFET Input Op Amp Low Noise, Picoampere Bias Current Op Amp Low Noise, 325MHz Rail-to-Rail Input and Output Op Amp Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps COMMENTS Lowest Noise 0.85nV/Hz 0.002% THD, Max Noise 1.2nV/Hz Similar to LT1007 Similar to LT1037 1GHz, 2.6nV/Hz, Gain of 25 Stable Precision C-LoadTM Stable Rail-to-Rail 3.2nV/Hz 4.2nV/Hz, 10fA/Hz 6nV/Hz, 1fA/Hz, IB = 10pA Max 3.5nV/Hz CLOAD to 1000pF, IB = 200pA Max 2.2MHz Bandwidth, 1.2V/s SR
sn16789 16789fs
C-Load is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
www.linear.com
+
100k
+
-
-
U
7V LT1461-5 10F 0.1F VREF 10 REF+ 1k 0.1% 1F 1k 0.1% 1F REF - 10 100 100 IN+ LTC2440 IN- 1/2 LT1678 0.047F 0.047F 1/2 LT1678 1 2 2s
16789 TA02
LT/TP 0104 1K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2003

▲Up To Search▲

Price & Availability of LT1679

	To Download LT1679 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .