DESCRIPTION FEATURES TYPICAL APPLICATION. LT1097 Low Cost, Low Power Precision Op Amp APPLICATIONS

Transcription

1 LT97 Low Cost, Low Power Precision Op Amp FEATRES Offset Voltage µv Max Offset Voltage Drift µv/ C Max Bias Current pa Max Offset Current pa Max Bias and Offset Current Drift pa/ C Max Supply Current µa Max.Hz to Hz Noise.µVp-p,.pAp-p CMRR db Min Voltage Gain 7dB Min PSRR db Min Guaranteed Operation on Two NiCad Batteries APPLICATIONS Replaces OP-7/OP-77/OP-97/OP-77/AD77/ LT with Improved Price/Performance High Impedance Difference Amplifiers Logarithmic Amplifiers (Wide Dynamic Range) Thermocouple Amplifiers Precision Instrumentation Active Filters (with Small Capacitors) DESCRIPTION LT 97 achieves a new standard in combining low price and outstanding precision performance. On all operational amplifier data sheets, the specifications listed on the front page are for highly selected, expensive grades, while the specs for the low cost grades are buried deep in the data sheet. The LT97 does not have any selected grades, the outstanding specifications shown in the Features section are for its only grade. The design effort of the LT97 concentrated on optimizing the performance of all precision specs at only µa of supply current. Typical values are µv offset voltage, pa bias and offset currents,.µv/ C and.pa/ C drift. Common mode and power supply rejections, voltage gain are typically in excess of 8dB. All parameters that are important for precision, low power op amps have been optimized. Consequently, using the LT97 error budget calculations in most applications is unnecessary., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION Saturated Standard Cell Amplifier Input Offset Voltage Distribution.8V N9 SATRATED STANDARD CELL # EPPLEY LABS NEWPORT, R. I. 7 R k LT97 R 9V =.V TO 8.V AS.8k R k THE TYPICAL pa BIAS CRRENT OF THE LT97 WILL DEGRADE THE STANDARD CELL BY ONLY ppm/year. NOISE IS A FRACTION OF A ppm. NPROTECTED GATE MOSFET ISOLATES STANDARD CELL ON POWER DOWN. LT97 TA PERCENT OF NITS, NITS IN SO PACKAGE,8 NITS IN PLASTIC DIP,8 NITS TESTED INPT OFFSET VOLTAGE (µv) LT97 G

2 LT97 ABSOLTE MAXIMM RATINGS W W W Supply Voltage... ±V Differential Input Current (Note )... ±ma Input Voltage... ±V Output Short Circuit Duration... Indefinite Operating Temperature Range... C to 8 C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... C PACKAGE/ORDER INFORMATION W V OS TRIM IN IN V TOP VIEW 8 7 V OS TRIM V OVER COMP ORDER PART NMBER LT97CN8 V OS TRIM IN IN V TOP VIEW 8 7 V OS TRIM V OVER COMP ORDER PART NMBER LT97S8 N8 PACKAGE 8-LEAD PLASTIC DIP S8 PACKAGE 8-LEAD PLASTIC SO ELECTRICAL CHARACTERISTICS, V CM = V,, unless otherwise noted. LT97CN8 LT97S8 SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage µv V OS Long Term Input Offset.. µv/mo TIME Voltage Stability I OS Input Offset Current pa I B Input Bias Current ± ± ± ± pa e n Input Noise Voltage.Hz to Hz.. µvp-p Input Noise Voltage Density f O = Hz nv/ Hz f O = Hz nv/ Hz i n Input Noise Current.Hz to Hz.. pap-p Input Noise Current Density f O = Hz.. pa/ Hz f O = Hz.8.8 pa/ Hz Input Resistance (Note ) Differential Mode 8 7 MΩ Common Mode 8 Ω Input Voltage Range ±. ±. ±. ±. V CMRR Common Mode Rejection Ratio V CM = ±.V db PSRR Power Supply Rejection Ratio V S = ±.V to ±V db A VOL Large Signal Voltage Gain V O = ±V, R L = k 7 7 V/mV V O = ±V, R L = k V/mV V Output Voltage Swing R L = k ± ±.8 ± ±.8 V R L = k ±. ± ±. ± V SR Slew Rate.... V/µs GBW Gain Bandwidth Product 7 7 khz I S Supply Current µa Offset Adjustment Range R POT = k, Wiper to V ± ± µv Minimum Supply Voltage (Note ) ±. ±. V

3 ELECTRICAL CHARACTERISTICS, V CM = V, C T A 7 C, unless otherwise noted. LT97 LT97CN8 LT97S8 SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage µv Average Temperature Coefficient of (Note )... µv/ C Input Offset Voltage I OS Input Offset Current 7 7 pa Average Temperature Coefficient of (Note ).. pa/ C Input Offset Current I B Input Bias Current ± ± ±7 ±7 pa Average Temperature Coefficient of (Note ).. pa/ C Input Bias Current A VOL Large Signal Voltage Gain V = ±V, R L k V/mV V = ±V, R L k V/mV CMRR Common Mode Rejection Ratio V CM = ±.V 8 8 db PSRR Power Supply Rejection Ratio V S = ±.V to ±V 8 8 db Input Voltage Range ±. ±. ±. ±. V V Output Voltage Swing R L = k ± ±.7 ± ±.7 V I S Supply Current µa ELECTRICAL CHARACTERISTICS, V CM = V, C T A 8 C, unless otherwise noted. (Note ) LT97CN8 LT97S8 SYMBOL PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage 7 µv Average Temperature Coefficient of.... µv/ C Input Offset Voltage I OS Input Offset Current pa Average Temperature Coefficient of.. pa/ C Input Offset Current I B Input Bias Current ±7 ± ±8 ±7 pa Average Temperature Coefficient of.. pa/ C Input Bias Current A VOL Large Signal Voltage Gain V = ±V, R L k 7 7 V/mV V = ±V, R L k 7 7 V/mV CMRR Common Mode Rejection Ratio V CM = ±.V db PSRR Power Supply Rejection Ratio V S = ±.V to ±V db Input Voltage Range ±. ± ±. ± V V Output Voltage Swing R L = k ± ±. ± ±. V I S Supply Current 8 8 µa The denotes specifications which apply over the full operating temperature range. Note : Differential input voltages greater than V will cause excessive current to flow through the input protection diodes unless limiting resistance is used. Note : This parameter is guaranteed by design and is not tested. Note : Power supply rejection ratio is measured at the minimum supply voltage. Note : This parameter is not % tested. Note : The LT97 is designed, characterized and expected to meet these extended temperature limits, but is not tested at C and 8 C. Guaranteed I grade parts are available; consult factory.

4 LT97 TYPICAL PERFORMANCE CHARACTERISTICS W Distribution to Offset Voltage Drift with Temperature PERCENT OF NITS NITS TESTED IN N8 PACKAGES FROM SIX RNS OFFSET VOLTAGE DRIFT WITH TEMPERATRE (µv/ C) LT97 G INPT BIAS CRRENT (pa) Input Bias Current vs Temperature NDERCANCELLED NIT OVERCANCELLED NIT 7 TEMPERATRE ( C) 97 G COMMON MODE RANGE OR PT SWING (V) V V. V. V. V.8 V.8 V. V. V. Minimum Supply Voltage, Common Mode Range and Voltage Swing at V MIN CM RANGE CM RANGE SWING SWING R L = k V 8 TEMPERATRE ( C) 97 G ±. ±. ±. ±.8 MINIMM SPPLY VOLTAGE, V MIN (V) Warm-p Drift Input Bias Current Over Common Mode Range CHANGE IN OFFSET VOLTAGE (µv) PLASTIC-IN-LINE PACKAGE PLASTIC (N) OR SO (S) INPT BIAS CRRENT (pa) 8 8 DEVICE WITH POSITIVE INPT CRRENT R IN CM = Ω DEVICE WITH NEGATIVE INPT CRRENT V CM I B TIME AFTER POWER ON (MINTES) 97 G COMMON MODE INPT VOLTAGE 97 G

5 LT97 TYPICAL PERFORMANCE CHARACTERISTICS W Output Short Circuit Current vs Time SHORT CIRCIT CRRENT (ma) SINKING SORCING TIME FROM PT SHORT (MINTES) 97 G7.Hz to Hz Noise.Hz to Hz Noise NOISE VOLTAGE (.µv/div) V S = ±.V TO ±V NOISE VOLTAGE (.µv/div).µv V S = ±.V TO ±V 8 TIME (SECONDS) 97 G8 8 TIME (SECONDS) 97 G9 VOLTAGE NOISE DENSITY (nv Hz) CRRENT NOISE DENSITY (fa Hz) Noise Spectrum V S = ±.V TO ±V /f CORNER.Hz CRRENT NOISE VOLTAGE NOISE /f CORNER Hz FREQENCY (Hz) CHANGE IN OFFSET VOLTAGE (µv) Voltage Gain V s = ± V R L = k R L = k R L = k R L = k PT VOLTAGE (V) 97 G 97 G

6 LT97 TYPICAL PERFORMANCE CHARACTERISTICS W Voltage Gain vs Frequency VOLTAGE GAIN (db) 8.. k k k M M FREQENCY (Hz) 97 G GAIN (db) POWER SPPLY REJECTION RATIO (db). 8 Gain, Phase Shift vs Frequency GAIN PHASE 8 PHASE MARGIN = 7 C. FREQENCY (MHz) Power Supply Rejection vs Frequency POSITIVE SPPLY 97 G NEGATIVE SPPLY. k k k M FREQENCY (Hz) 97 G PHASE SHIFT (DEGREES) COMMON MODE REJCTION RATIO (db) SLEW RATE (V/µs) 8.. Common Mode Rejection vs Frequency k k k M FREQENCY (Hz) Slew Rate, Gain Bandwidth Product vs Overcompensation Capacitor SLEW 97 G GBW. OVERCOMPENSATION CAPACITOR (pf) 97 G GAIN BANDWIDTH PRODCT (khz)

7 LT97 TYPICAL PERFORMANCE CHARACTERISTICS W Small Signal Transient Response Large Signal Transient Response mv/div V/DIV A V =, C LOAD = pf, µs/div 97 G7 A V =, µs/div 97 G8 Capacitive Load Handling OVERSHOOT (%) 7 C S : PIN TO GROND A V = C S = pf A V = C S = A V = C S =, CAPACITIVE LOAD (pf) 97 G9 7

8 SCHEMATIC DIAGRAM W W LT97 TRIM TRIM 8 OVER COMP V 7 8Ω 8Ω µa k µa k.k pf.k.k Q Q9 8µA.k Q Q Q Q Q7 Q9 Q Q Q8 Q7 Q S k Q Ω Ω IN S S S Q Q Q Q9 Q Q k.k Q J Q8 Q.k Q8 Q Ω Q IN Q µa Q.7k Q7 8µA Q µa µa Q Q Q V.7k.7k k Ω Ω QQ ARE SPERGAIN TRANSISTORS 97 BD 8

9 LT97 APPLICATIONS INFORMATION W The LT97 is pin compatible to and directly replaces such precision op amps as the OP-7, OP-77, AD77, OP-97, OP- 77, LM7 and LT with improved price/performance. Compatibility includes externally nulling the offset voltage, as all of the above devices are trimmed with a potentiometer between Pin and Pin 8 and the wiper tied to V. The simple difference amplifier can be used to illustrate the all-around excellence of the LT97. The k input resistance is selected to be large enough compared to input signal source resistance. Simultaneously, the k resistors should not dominate the precision and noise error budget. Assuming perfect matching between the four resistors, the following table summarizes the input referred performance obtained using the LT97 and other popular, low cost precision op amps. Input offset voltage can be adjusted over a ±µv range with a k potentiometer. The LT97 is internally compensated for unity gain stability. As shown on the Capacitive Load Handling plot, the LT97 is stable with any capacitive load. However, the overcompensation capacitor, C S, can be used to reduce overshoot with heavy capacitive loads, to narrow noise bandwidth or to stabilize circuits with gain in the feedback loop. ±7V Common Mode Range Difference Amplifier Frequency Compensation and Optional Offset Nulling IN IN k k k V 7 LT97 k POT LT C S V k V V LT97 F LT97 F Guaranteed Perfomance,, PARAMETER LT97CN8 OP-77GP AD77JN OP-77GP OP-97FP NITS Error Terms V OS Max 9 7 µv I OS Max k 7 7 µv Gain Min, V Out µv CMRR, Min, ±V In 9 µv PSRR, Min, ±% µv Sum of All Error Terms µv.hz to Hz Noise Voltage Noise µvp-p Typ Current Noise k µvp-p Typ Resistor Noise..... µvp-p Typ RMS sum µvp-p Drift with Temp TCV OS Max.. µv/ C TCI OS Max k.... µv/ C Sum of Drift Terms.... µv/ C Supply Current Max.. ma 9

10 LT97 APPLICATIONS INFORMATION W The availability of the compensation terminal permits the use of feedforward frequency compensation to enhance slew rate. The voltage follower feedforward scheme bypasses the amplifier s gain stages and slews at nearly V/µs. The inputs of the LT97 are protected with back-to-back diodes. In the voltage follower configuration, when the input is driven by a fast, large signal pulse (>V), the input protection diodes effectively short the output to the input during slewing, and a current, limited only by the output short circuit protection will flow through the diodes. The use of a feedback resistor, as shown in the voltage follower feedforward diagram, is recommended because this resistor keeps the current below the short circuit limit, resulting in faster recovery and settling of the output. Follower Feedforward Compensation pf Pulse Response of Feedforward Compensation Test Circuit for Offset Voltage and its Drift with Temperature k* IN k k LT97.µF V/DIV µs/div 97 G Ω* k* V 7 LT97 V V O = V OS V O LT97 F *RESISTORS MST HAVE LOW THERMOELECTRIC POTENTIAL LT97 F TYPICAL APPLICATIO Low Power Comparator with <µv Hysteresis V IN k IN k k k 7 LT97 k k k N9 V LT97 TA

11 LT97 PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow.) (LTC DWG # -8-).* (.) MAX 8 7. ±.* (.77 ±.8).. (7. 8.).. (..). ±. (. ±.7).9. (.9.8) ( ). (.) TYP. ±. (. ±.) *THESE DIMENSIONS DO NOT INCLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. INCH (.mm). (.7) MIN.8 ±. (.7 ±.7). (.8) MIN N8 97 S8 Package 8-Lead Plastic Small Outline (Narrow.) (LTC DWG # -8-).89.97* (.8.) (.79.97)..7** (.8.988).8. (..).. (..8) 8 TYP..9 (..7).. (..) (..8) * DIMENSION DOES NOT INCLDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED." (.mm) PER SIDE ** DIMENSION DOES NOT INCLDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED." (.mm) PER SIDE. (.7) TYP 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. SO8 99

12 LT97 TYPICAL APPLICATIO Input Amplifier for / Digit Voltmeter IN 9M V 9k 9k.V V V k % pf V FN7 k ALLEN BRADLEY DECADE VOLTAGE DIVIDER LT97 V 7 V 9k* k* *RATIO MATCH ±.% V.V V V V TO V FLL SCALE ANALOG DIGITAL CONVERTER THIS APPLICATION REQIRES LOW BIAS CRRENT AND OFFSET VOLTAGE, LOW NOISE, AND LOW DRIFT WITH TIME AND TEMPERATRE. LT97 TA RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT9/LT9 Dual/Quad General Purpose Micropower Rail-to-Rail Op Amps Over-The-Top TM Inputs, µa Supply Current Per Amplifier, V to V Supply Range, 8kHz GBW LT9/LT9 Dual/Quad MHz Low Power Single Supply Op Amps 8µV V OS Max, V/µs Slew Rate, µa Supply Per Amplifier LT77 Single Micropower Low V OS Op Amp µv V OS Max, 8µA Supply Current, khz GBW, Optimized for V Supplies Over-The-Top is a trademark of Linear Technology Corporation. Linear Technology Corporation McCarthy Blvd., Milpitas, CA 9-77 (8) -9 FAX: (8) -7 TELEX: fas sn97 LT/TP 98 K REV A PRINTED IN SA LINEAR TECHNOLOGY CORPORATION 989