Datasheet

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LTC1250

1250fb

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

trademarks are the property of their respective owners. Protected by U.S. Patents

including 4933642.

–

–5V

1000pF

18.2k

1000pF

18.2k

–5V

0.1µF

= 100

1250 TA01

350Ω

STRAIN

GAUGE

50Ω

GAIN

TRIM

LTC1250

TIME (s)

µV

LT1250 TA02

–1

–2

= ±5V

= 10k

TYPICAL APPLICATIO

APPLICATIO S

DESCRIPTIO

FEATURES

Very Low Noise

Zero-Drift Bridge Amplifier

■

Electronic Scales

■

Strain Gauge Amplifiers

■

Thermocouple Amplifiers

■

High Resolution Data Acquisition

■

Low Noise Transducers

■

Instrumentation Amplifiers

■

Very Low Noise: 0.75µV

P-P

Typ, 0.1Hz to 10Hz

■

DC to 1Hz Noise Lower Than OP-07

■

Full Output Swing into 1k Load

■

Offset Voltage: 10µV Max

■

Offset Voltage Drift: 50nV/°C Max

■

Common Mode Rejection Ratio: 110dB Min

■

Power Supply Rejection Ratio: 115dB Min

■

No External Components Required

■

Pin Compatible with Standard 8-Pin Op Amps

■

Available in Standard 8-Pin Plastic DIP

and 8-Pin SO Packages

The LTC

1250 is a high performance, very low noise zero-

drift operational amplifier. The LTC1250’s combination of

low front-end noise and DC precision makes it ideal for use

with low impedance bridge transducers. The LTC1250

features typical input noise of 0.75µV

P-P

from 0.1Hz to

10Hz, and 0.2µV

P-P

from 0.1Hz to 1Hz. The LTC1250 has

DC to 1Hz noise of 0.35µV

P-P

, surpassing that of low noise

bipolar parts including the OP-07, OP-77, and LT1012.

The LTC1250 uses the industry-standard single op amp

pinout, and requires no external components or nulling

signals, allowing it to be a plug-in replacement for bipolar

op amps.

The LTC1250 incorporates an improved output stage

capable of driving 4.3V into a 1k load with a single 5V

supply; it will swing ±4.9V into 5k with ±5V supplies. The

input common mode range includes ground with single

power supply voltages above 12V. Supply current is 3mA

with a ±5V supply, and overload recovery times from

positive and negative saturation are 0.5ms and 1.5ms,

respectively. The internal nulling clock is set at 5kHz for

optimum low frequency noise and offset drift; no external

connections are necessary.

The LTC1250 is available in a standard 8-pin plastic DIP

and 8-pin SO packages.

Input Referred Noise 0.1Hz to 10Hz

Differential Bridge Amplifier

Summary of content (12 pages)

PAGE 1
LTC1250 Very Low Noise Zero-Drift Bridge Amplifier U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®1250 is a high performance, very low noise zerodrift operational amplifier. The LTC1250’s combination of low front-end noise and DC precision makes it ideal for use with low impedance bridge transducers. The LTC1250 features typical input noise of 0.75µVP-P from 0.1Hz to 10Hz, and 0.2µVP-P from 0.1Hz to 1Hz. The LTC1250 has DC to 1Hz noise of 0.
PAGE 2
LTC1250 W W U W ABSOLUTE AXI U RATI GS (Note 1) Total Supply Voltage (V + to V –) ............................. 18V Input Voltage ........................ (V + + 0.3V) to (V – – 0.3V) Output Short Circuit Duration ......................... Indefinite Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C Operating Temperature Range LTC1250M (OBSOLETE) ............ – 55°C to 125°C LTC1250C ..........................................
PAGE 3
LTC1250 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, VIN = ±5V, otherwise specifications are at TA SYMBOL PARAMETER CONDITIONS fS VOS ∆VOS en Internal Sampling Frequency Input Offset Voltage Average Input Offset Drift Input Noise Voltage (Note 3) IB IOS Input Bias Current Input Offset Current Maximum Output Voltage Swing TA = 25°C TA = 25°C (Note 2) (Note 2) TA = 25°C, 0.1Hz to 10Hz TA = 25°C, 0.
PAGE 4
LTC1250 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Noise vs Temperature 8 4.5 1.2 7 SAMPLING FREQUENCY (kHz) 1.0 4.0 SUPPLY CURRENT (mA) 0.8 0.1Hz TO 10Hz 0.6 0.4 0.1Hz TO 1Hz 3.5 3.0 2.5 0.2 50 25 75 0 TEMPERATURE (°C) 100 2.
PAGE 5
LTC1250 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Swing vs Load Resistance, Dual Supplies Transient Response Output Voltage Swing vs Load Resistance, Single Supply 10 18 RL TO GND 9 14 7 OUTPUT SWING (V) OUTPUT SWING (±V) 2V/DIV 8 6 VS = ±5V 5 4 VS = ±2.
PAGE 6
LTC1250 W U U UO APPLICATI S I FOR ATIO Input Noise The LTC1250, like all CMOS amplifiers, exhibits two types of low frequency noise: thermal noise and 1/f noise. The LTC1250 uses several design modifications to minimize these noise sources. Thermal noise is minimized by raising the gM of the front-end transistors by running them at high bias levels and using large transistor geometries.
PAGE 7
LTC1250 W U U UO APPLICATI S I FOR ATIO LTC1250 and on the PC board, play an increasing role. Low value resistors (below 5k) may not require a capacitor at all. Input Bias Current The inputs of the LTC1250, like all zero-drift op amps, draw only small switching spikes of AC bias current; DC leakage current is negligible except at very high temperatures.
PAGE 8
LTC1250 U W U UO APPLICATI S I FOR ATIO Single Supply Operation The LTC1250 will operate with single supply voltages as low as 4.5V, and the output swings to within millivolts of either supply when lightly loaded. The input stage will common mode to within 250mV of ground with a single 5V supply, and will common mode to ground with single supplies above 11V.
PAGE 9
LTC1250 U PACKAGE DESCRIPTIO J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION 0.005 (0.127) MIN 0.405 (10.287) MAX 8 7 6 5 0.025 (0.635) RAD TYP 0.220 – 0.310 (5.588 – 7.874) 1 0.300 BSC (0.762 BSC) 2 3 4 0.200 (5.080) MAX 0.015 – 0.060 (0.381 – 1.524) 0.008 – 0.018 (0.203 – 0.457) 0.385 ± 0.025 (9.779 ± 0.635) 0° – 15° 0.045 – 0.
PAGE 10
LTC1250 U PACKAGE DESCRIPTIO N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) +.035 .325 –.015 ( 8.255 +0.889 –0.381 ) .045 – .065 (1.143 – 1.651) .130 ± .005 (3.302 ± 0.127) .065 (1.651) TYP .100 (2.54) BSC .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 NOTE: 1.
PAGE 11
LTC1250 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 8 .245 MIN 7 6 5 .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) .008 – .010 (0.203 – 0.254) .053 – .069 (1.346 – 1.752) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN .014 – .019 (0.355 – 0.
PAGE 12
LTC1250 UO TYPICAL APPLICATI S Differential Thermocouple Amplifier Reference Buffer 15V 7.5k 3 3 1 7 + LTC1250 2 LM399 – R1 10k 0.1% 6 5V 2 7 – LTC1250 4 3 4 R3 1M 0.1% C1 100pF – 2 + R2 10k 0.1% TYPE K † 1250 TA03 C2 100pF 5V 10mV/°C VOUT LT1025 GND R7 500Ω FULL-SCALE TRIM R8 5k 1% R5 3k VIN VOUT 100mV/°C R6 7.5k 1% 4 –5V R4 1M 0.1% VCM ±10ppm ERROR AT ±15mA 1µVP-P OUTPUT NOISE 2.