Datasheet

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LT1678/LT1679

sn16789 16789fs

FEATURES

APPLICATIO S

DESCRIPTIO

TYPICAL APPLICATIO

Dual/Quad Low Noise,

Rail-to-Rail, Precision Op Amps

■

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: 100µV Max

■

Low Input Bias Current: 20nA Max

■

High A

VOL

: 3V/µV Min, R

= 10k

■

High CMRR: 100dB Min

■

High PSRR: 106dB Min

■

Gain Bandwidth Product: 20MHz

■

Operating Temperature Range: –40°C to 85°C

■

Matching Specifications

■

No Phase Inversion

■

8-Lead SO and 14-Lead SO Packages

The LT

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: 100µV 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 appli-

cations such as a two op amp instrumentation amplifier

design. The LT1678/LT1679 are specified for supply volt-

ages of ±15V, single 5V as well as single 3V. For a single

amplifier with similiar performance, see the LT1677 data

sheet.

Instrumentation Amplifier with Shield Driver

■

Strain Gauge Amplifiers

■

Portable Microphones

■

Battery-Powered Rail-to-Rail Instrumentation

■

Low Noise Signal Processing

■

Microvolt Accuracy Threshold Detection

■

Infrared Detectors

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

0.1Hz to 10Hz Voltage Noise

–

1/4

LT1679

16789 TA01

–

1/4

LT1679

1/4

LT1679

–15V

15V

OUTPUT

1/4

LT1679

30k1k

3.4k

100Ω

3.4k

30k

–

INPUT

GUARD

100Ω

–

GAIN = 1000

TIME (sec)

VOLTAGE NOISE (50nV/DIV)

16789 TA01b

= ±2.5V

4681002

Downloaded from Arrow.com.

Summary of content (16 pages)

PAGE 1
LT1678/LT1679 Dual/Quad Low Noise, Rail-to-Rail, Precision Op Amps U FEATURES DESCRIPTIO ■ The LT ®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: 100µV maximum offset voltage, greater than 100dB common mode and power supply rejection and 20MHz gain bandwidth product.
PAGE 2
LT1678/LT1679 W W W AXI U U ABSOLUTE RATI GS (Note 1) 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 ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................. 300°C Operating Temperature Range (Note 4) ...........................
PAGE 3
LT1678/LT1679 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 6) IOS Input Offset Current (Note 11) 0°C ≤ TA ≤ 70°C – 40°C ≤ TA ≤ 85°C TYP MAX ● ● 4 5 8 25 35 55 nA nA nA VS = 5V, VCM = VS + 0.1V VS = 5V, VCM = VS – 0.3V, 0°C ≤ TA ≤ 70°C ● VS = 5V, VCM = VS – 0.
PAGE 4
LT1678/LT1679 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 6) VOL Output Voltage Swing Low (Note 11) Above GND ISINK = 2.
PAGE 5
LT1678/LT1679 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = ±15V, VCM = VO = 0V unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage CONDITIONS (Note 6) TYP MAX UNITS ● ● 20 30 45 150 350 420 µV µV µV ● 0.
PAGE 6
LT1678/LT1679 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = ±15V, VCM = VO = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 6) VOL Output Voltage Swing Low Above – VS ISINK = 0.
PAGE 7
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.
PAGE 8
LT1678/LT1679 U W TYPICAL PERFOR A CE CHARACTERISTICS Voltage Noise vs Temperature Input Bias Current vs Temperature Current Noise vs Frequency 10 VS = ±15V VCM = 0V NOISE VOLTAGE (pA/√Hz) 5 10Hz 4 1kHz 3 2 16 VS = ±15V TA = 25°C 14 VCM = 0V 1 VCM = 14.5V 8 6 4 2 0 –4 50 25 0 75 TEMPERATURE (°C) –25 100 0.1 0.01 125 0.1 1 FREQUENCY (kHz) Input Bias Current Over the Common Mode Range INPUT BIAS CURRENT (nA) 800 600 400 VCM = 14.
PAGE 9
LT1678/LT1679 U W TYPICAL PERFOR A CE CHARACTERISTICS Common Mode Range vs Temperature 500 400 3 300 2 200 25°C –55°C 1 100 –55°C 125°C 0 0 25°C –1 –100 VOS IS REFERRED TO VCM = 0V –2 –3 –200 –300 125°C –400 –4 –5 –1.0 –500 V– 1.0 2.0 –0.8 –0.4 V – 0.4 VCM – VS+ (V) VCM – VS– (V) 3.5 3.0 TA = 125°C 2.5 TA = 25°C 2.0 TA = –55°C 1.5 1.0 0 ±5 ±10 ±15 SUPPLY VOLTAGE (V) COMMON MODE REJECTION RATIO (dB) 4 160 4.0 SUPPLY CURRENT PER AMPLIFIER (mA) VS = ±2.
PAGE 10
LT1678/LT1679 U W TYPICAL PERFOR A CE CHARACTERISTICS Settling Time vs Output Step (Inverting) Settling Time vs Output Step (Noninverting) 5k VIN – VOUT 4 3 0.01% OF FULL SCALE 0.01% OF FULL SCALE 2 1 0.1% OF FULL SCALE 0.1% OF FULL SCALE 0 –10 –8 –6 –4 –2 0 2 4 OUTPUT STEP (V) 6 8 VIN VOUT + RL = 1k 4 0.01% OF FULL SCALE 3 0.
PAGE 11
LT1678/LT1679 U W U U 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.
PAGE 12
LT1678/LT1679 U W U U APPLICATIO S I FOR ATIO 100 0.1µF 90 100k GAIN (dB) 10Ω 80 – 2k * LT1678 + + 4.3k 22µF SCOPE ×1 RIN = 1M LT1001 4.7µF – VOLTAGE GAIN = 50,000 2.2µF 24.3k 60 50 110k 40 100k *DEVICE UNDER TEST NOTE: ALL CAPACITOR VALUES ARE FOR NONPOLARIZED CAPACITORS ONLY 70 30 0.01 0.1µF 16789 F03 0.1 1 10 FREQUENCY (Hz) 100 16789 F04 Figure 4. 0.1Hz to 10Hz Peak-to-Peak Noise Tester Frequency Response Figure 3. 0.1Hz to 10Hz Noise Test Circuit 3.
PAGE 13
LT1678/LT1679 U W U U APPLICATIO S I FOR ATIO Rail-to-Rail Input Rail-to-Rail Output 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).
PAGE 14
Q13 ×2 IA R21 100Ω R24 100Ω Q24 Q8 Q9 R9 200Ω Q3 Q1B IC Q2A Q10 Q2B RC2 6k Q6 Q4 ID 50µA Q11 Q7 IA, IB = 0µA VCM > 1.5V ABOVE –VS IC = 200µA VCM < 0.7V BELOW +VS ID = 100µA VCM < 0.7V BELOW +VS 200µA VCM < 1.5V ABOVE –VS 50µA VCM > 0.7V BELOW +VS 0µA VCM > 0.
PAGE 15
LT1678/LT1679 U PACKAGE DESCRIPTIO S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 7 8 .245 MIN 5 6 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) 3 2 4 .053 – .069 (1.346 – 1.752) .008 – .010 (0.203 – 0.254) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) .
PAGE 16
LT1678/LT1679 U 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 VREF 7V φ1 5,6,7,8 LT1461-5 2 10µF 0.1µF 5V + 100k 10Ω 1 1/2 LT1678 – 0.047µF 350Ω 350Ω 350Ω 350Ω VREF 100k 3 4 5,6,7,8 2 100Ω IN+ 1µF 100Ω 0.1% – REF+ 1k 0.1% 1k 0.1% LTC2440 100Ω IN– 1µF 0.