Features Appications LT3X High Temperature 7 C Dua MHz, Rai-to-Rai Input and Output, Utraow.9nV/ Hz Noise, Low Power Op Amp Description Extreme High Temperature Operation: C to 7 C Low Noise Votage:.9nV/ Hz (khz) Low Suppy Current: 3mA/Amp Max Gain Bandwidth Product: MHz Low Distortion: 8 at MHz Low Offset Votage: µv Max Wide Suppy Range:.V to.v Inputs and Outputs Swing Rai-to-Rai Common Mode Rejection Ratio 9 Typ Low Noise Current:.pA/ Hz Output Current: 3mA Min 8-Pin SO Package Avaiabe as Dice Down Hoe Driing and Instrumentation Heavy Industria Avionics High Temperature Environments Low Noise, Low Power Signa Processing Active Fiters Rai-to-Rai Buffer Ampifiers Driving A/D Converters DSL Receivers Battery Powered/Battery Backed Equipment The LT 3X is a dua ow noise, rai-to-rai input and output unity gain stabe op amp that features.9nv/ Hz noise votage and draws ony.ma of suppy current per ampifier. These ampifiers combine very ow noise and suppy current with a MHz gain bandwidth product, a V/µs sew rate, and are optimized for ow suppy signa conditioning systems. These ampifiers maintain their performance for suppies from.v to.v and are specified at 3V, V and ±V suppies. Harmonic distortion is ess than 8c at MHz making these ampifiers suitabe in ow power data acquisition systems. These devices can be used as pug-in repacements for many op amps to improve input/output range and noise performance. The LT3X is a member or a growing series of high temperature quaified products offered by Linear Technoogy. For a compete seection of high temperature products, pease consut our website, www.inear.com. The LT3X comes in an 8-pin SO package with standard dua op amp pinout. The LT3X is aso avaiabe as dice. L, LT, LTC, LTM, Linear Technoogy and the Linear ogo are registered trademarks of Anaog Devices, Inc. A other trademarks are the property of their respective owners. Typica Appication Low Noise Differentia Ampifier with Gain Adjust and Common Mode Contro V IN V IN R Ω R Ω R3 Ω R Ω R Ω R Ω / LT3X C 7pF R7, Ω V R8 Ω V R A C pf R9 Ω R B.µF / LT3X C3 pf R, Ω V OUT V OUT R OUTPUT V B CM = V R A R B LT3X TAa For more information www.inear.com/lt3x RELATIVE DIFFERENTIAL GAIN (/DIV) Low Noise Differentia Ampifier Frequency Response k M ( ) G = G = G = LT3X TAb M 3xf
LT3X Absoute Maximum Ratings (Note ) Tota Suppy Votage (V to V )...V Input Current (Note )... ±ma Output Short-Circuit Duration (Note 3)...Thermay Limited Operating Temperature Range (Note ) LT3X... C to 7 C Junction Temperature... C Storage Temperature Range... C to C Lead Temperature (Sodering, sec)...3 C Pin Configuration OUT A IN A IN A V 3 TOP VIEW 8 7 S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = C, θ JA = 9 C/W V OUT B IN B IN B Order Information (http://www.inear.com/product/lt3x#orderinfo) SPECIFIED LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3XS8#PBF LT3XS8#TRPBF 3X 8-Lead Pastic SO C to 7 C *The temperature grade is identified by a abe on the shipping container For more information on ead free part marking, go to: http://www.inear.com/eadfree/ For more information on tape and ree specifications, go to: http://www.inear.com/tapeandree/. Some packages are avaiabe in unit rees through designated saes chaes with #TRMPBF suffix. Eectrica Characteristics uness otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V OS Input Offset Votage V S = V, V, V CM = Haf Suppy.. V S = 3V, V, V CM = Haf Suppy.. V S = V, V, V CM = V to V.. V S = 3V, V, V CM = V to V. 3. Input Offset Votage Match (Chae-to-Chae) (Note ), V S =V, V; V S = 3V, V; V CM = V OUT = haf suppy, V CM = Haf Suppy. V CM = V to V.3 I B Input Bias Current V CM = Haf Suppy 7..3 V CM = V.3. V CM = V 8.8 3.3 I B I B Shift V CM = V to V.7.3 I B Match (Chae-to-Chae) (Note )...8.8 For more information www.inear.com/lt3x 3xf
Eectrica Characteristics uness otherwise noted. LT3X SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I OS Input Offset Current V CM = Haf Suppy V CM = V V CM = V Input Noise Votage.Hz to Hz 8 nv P-P e n Input Noise Votage Density f = khz, V S = V nv/ Hz f = khz, V S = V.9. nv/ Hz i n Input Noise Current Density, Baanced Input Noise Current Density, Unbaanced Input Resistance..7. f = khz, V S = V.7. Common Mode Differentia Mode C IN Input Capacitance Common Mode Differentia Mode A VOL Large Signa Gain V S = V, V O =.V to.v, to V S / V S = V, V O = V to V, R L = to V S / V S = 3V, V O =.V to.v, to V S / CMRR Common Mode Rejection Ratio V S = V, V CM = V to V V S = V, V CM =.V to 3.V V S = 3V, V CM = V to V 8. 7 8.8. 7 83 8. pa/ Hz pa/ Hz MΩ kω pf pf V/ V/ V/ CMRR Match (Chae-to-Chae) (Note ) V S = V, V CM =.V to 3.V 8 PSRR Power Suppy Rejection Ratio V S =.V to V, V CM = V 7 PSRR Match (Chae-to-Chae) (Note ) V S =.V to V, V CM = V 7 Minimum Suppy Votage (Note ). V V OL Output Votage Swing LOW Saturation (Note 7) V OH Output Votage Swing HIGH Saturation (Note 7) I SC Short-Circuit Current V S = V V S = 3V I S Suppy Current per Amp V S = V V S = 3V, V S =V, V; V S = 3V, V; V CM = V OUT = haf suppy, No Load I SINK = ma V S = V, I SINK = ma V S = 3V, I SINK = ma No Load I SOURCE = ma V S = V, I SOURCE = ma V S = 3V, I SOURCE = ma GBW Gain Bandwidth Product Frequency = MHz, V S = V 9 MHz SR Sew Rate V S = V, A V =,, V O = V 7 V/µs FPBW Fu Power Bandwidth (Note 9) V S = V, V OUT = 3V P-P.8. MHz t S Setting Time.%, V S = V, V STEP = V, A V =, 8 ns ±3 ± 8 8 9 3 ± ±..3 9 3 7 3..8 ma ma ma ma For more information www.inear.com/lt3x 3xf 3
LT3X Eectrica Characteristics The denotes the specifications which appy over C < T A < 7 C temperature range. V S = V, V; V S = 3V, V; V CM = V OUT = haf suppy, uness otherwise noted. (Note ) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V OS Input Offset Votage V S = V, V, V CM = Haf Suppy.. V S = 3V, V, V CM = Haf Suppy.. V S = V, V, V CM = V to V.. V S = 3V, V, V CM = V to V.. V OS TC Input Offset Votage Drift (Note 8) V CM = Haf Suppy 3. 9. µv/ C Input Offset Votage Match (Chae-to-Chae) (Note ) V CM = Haf Suppy V CM = V to V I B Input Bias Current V CM = Haf Suppy 7. V CM = V 7. V CM = V. I B I B Shift V CM = V to V.7. I B Match (Chae-to-Chae) (Note ).. I OS Input Offset Current V CM = Haf Suppy V CM = V V CM = V A VOL Large Signa Gain V S = V, V O =.V to.v, to V S / V S = V, V O =.V to 3.V, R L = to V S / V S = 3V, V O =.V to.v, to V S / CMRR Common Mode Rejection Ratio V S = V, V CM = V to V V S = V, V CM =.V to 3.V V S = 3V, V CM = V to V CMRR Match (Chae-to-Chae) (Note ) V S = V, V CM =.V to 3.V 8 PSRR Power Suppy Rejection Ratio V S = 3V to V, V CM = V 7 PSRR Match (Chae-to-Chae) (Note ) V S = 3V to V, V CM = V 7 Minimum Suppy Votage (Note ) 3. V V OL Output Votage Swing LOW Saturation (Note 7) V OH Output Votage Swing HIGH Saturation (Note 7) No Load I SINK = ma I SINK = ma I SC Short-Circuit Current V S = V V S = 3V I S Suppy Current per Amp V S = V V S = 3V No Load I SOURCE = ma V S = V, I SOURCE = ma V S = 3V, I SOURCE = ma GBW Gain Bandwidth Product Frequency = MHz 83 MHz SR Sew Rate V S = V, A V =,, V O = V 7 V/µs FPBW Fu Power Bandwidth (Note 9) V S = V, V OUT = 3V P-P.3.8 MHz 9 3.7 7 ± ±.3.7.3.3 3.3... 3 8 9 7 9 37 7 ± ±3 3.3 3......7 7 7 7..3 V/ V/ V/ ma ma ma ma For more information www.inear.com/lt3x 3xf
Eectrica Characteristics, ; V CM = V OUT = V, uness otherwise noted. LT3X SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V OS Input Offset Votage V CM = V V CM = V V CM = V Input Offset Votage Match (Chae-to-Chae) (Note ) I B Input Bias Current V CM = Haf Suppy V CM = V V CM = V...3 V CM = V. V CM = V to V. I B I B Shift V CM = V to V.3. I B Match (Chae-to-Chae) (Note ).. I OS Input Offset Current V CM = Haf Suppy V CM = V V CM = V Input Noise Votage.Hz to Hz 8 nv P-P e n Input Noise Votage Density f = khz.9 nv/ Hz f = khz.8. nv/ Hz i n Input Noise Current Density, Baanced Input Noise Current Density, Unbaanced Input Resistance 7. 9..3.3 3.8...3 f = khz.7. Common Mode Differentia Mode C IN Input Capacitance Common Mode Differentia Mode A VOL Large Signa Gain V O = ±.V, V O = ±.V, R L = CMRR Common Mode Rejection Ratio V CM = V to V V CM = V to V 7 8.8. 3 9 8 98..... 3...3 pa/ Hz pa/ Hz MΩ kω pf pf V/ V/ CMRR Match (Chae-to-Chae) (Note ) V CM = V to V 8 PSRR Power Suppy Rejection Ratio V S = ±.V to ±V 7 PSRR Match (Chae-to-Chae) (Note ) V S = ±.V to ±V 7 V OL Output Votage Swing LOW Saturation (Note 7) V OH Output Votage Swing HIGH Saturation (Note 7) No Load I SINK = ma I SINK = ma No Load I SOURCE = ma I SOURCE = ma I SC Short-Circuit Current ±3 ± ma I S Suppy Current per Amp.8 3. ma GBW Gain Bandwidth Product Frequency = MHz 7 MHz SR Sew Rate A V =,, V O = V 8 V/µs FPBW Fu Power Bandwidth (Note 9) V OUT = 3V P-P.9. MHz t S Setting Time.%, V STEP = V, A V =, 78 ns dg Differentia Gain (Note ) A V =, R F = R G = 99Ω, R L = k. % dp Differentia Phase (Note ) A V =, R F = R G = 99Ω, R L = k.3 DEG 87 9 3 9 9 For more information www.inear.com/lt3x 3xf
LT3X Eectrica Characteristics The denotes the specifications which appy over C < T A < 7 C temperature range. ; V CM = V OUT = V, uness otherwise noted. (Note ) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V OS Input Offset Votage V CM = V V CM = V V CM = V V OS TC Input Offset Votage Drift (Note 8) V CM = Haf Suppy 7. µv/ C Input Offset Votage Match (Chae-to-Chae) (Note ) V CM = V V CM = V to V I B Input Bias Current V CM = Haf Suppy 7.3 V CM = V. V CM = V 7. I B I B Shift V CM = V to V. I B Match (Chae-to-Chae) (Note ). 3. I OS Input Offset Current V CM = Haf Suppy V CM = V V CM = V A VOL Large Signa Gain V O = ±.V, V O = ±.V R L = CMRR Common Mode Rejection Ratio V CM = V to V V CM = V to V CMRR Match (Chae-to-Chae) (Note ) V CM = V to V 8 PSRR Power Suppy Rejection Ratio V S = ±.V to ±V 7 PSRR Match (Chae-to-Chae) (Note ) V S = ±.V to ±V 7 V OL Output Votage Swing LOW Saturation (Note 7) V OH Output Votage Swing HIGH Saturation (Note 7) No Load I SINK = ma I SINK = ma No Load I SOURCE = ma I SOURCE = ma I SC Short-Circuit Current ± ± ma I S Suppy Current per Amp 3.8.3 ma GBW Gain Bandwidth Product Frequency = MHz 9 MHz SR Sew Rate A V =,, V O = V 3 8 V/µs FPBW Fu Power Bandwidth (Note 9) V OUT = 3V P-P..9 MHz Note : Stresses beyond those isted under Absoute Maximum Ratings may cause permanent damage to the device. Exposure to any Absoute Maximum Rating condition for extended periods may affect device reiabiity and ifetime. Note : Inputs are protected by back-to-back diodes and diodes to each suppy. If the inputs are taken beyond the suppies or the differentia input votage exceeds.7v, the input current must be imited to ess than ma. Note 3: A heat sink may be required to keep the junction temperature beow the absoute maximum rating when the output is shorted indefinitey. Note : The LT3X is guaranteed to meet specified performance from C to 7 C. Note : Matching parameters are the difference between the two ampifiers of the LT3X. CMRR and PSRR match are defined as foows: CMRR and PSRR are measured in µv/v on the identica ampifiers. The difference is cacuated between the matching sides in µv/v. The resut is converted to..7 79.7 3.8 3..3...8...3. 3 8 9 7 98 7 3 3 3.7 9. 7.. 3...8.8 7 7 V/ V/ Note : Minimum suppy votage is guaranteed by power suppy rejection ratio test. Note 7: Output votage swings are measured between the output and power suppy rais. Note 8: This parameter is not % tested. Note 9: Fu-power bandwidth is cacuated from the sew rate: FPBW = SR/πV P Note : Differentia gain and phase are measured using a Tektronix TSGYC/NTSC signa generator and a Tektronix 78R Video Measurement Set. The resoution of this equipment is.% and.. Ten identica ampifier stages were cascaded giving an effective resoution of.% and.. For more information www.inear.com/lt3x 3xf
Typica Performance Characteristics LT3X NUMBER OF UNITS 3 3 V OS Distribution, V CM = V / V OS Distribution, V CM = V V OS Distribution, V CM = V V S = V, V S8 NUMBER OF UNITS VS = V, V 3 S8 NUMBER OF UNITS 3 V S = V, V S8 INPUT OFFSET VOLTAGE (µv) 8 8 INPUT OFFSET VOLTAGE (µv) 8 8 INPUT OFFSET VOLTAGE (µv) 3X G 3X G 3X G3 SUPPLY CURRENT (ma) 8 Suppy Current vs Suppy Votage (Both Ampifiers) T A = 7 C T A = C T A = C 8 TOTAL SUPPLY VOLTAGE (V) 3X G OFFSET VOLTAGE ()...... Offset Votage vs Input Common Mode Votage T A = 7 C T A = C T A = C V S = V, V TYPICAL PART 3 INPUT COMMON MODE VOLTAGE (V) 3X G INPUT BIAS CURRENT () Input Bias Current vs Common Mode Votage V S = V, V T A = C T A = C T A = 7 C 3 COMMON MODE VOLTAGE (V) 3X G INPUT BIAS CURRENT () 8 Input Bias Current vs Temperature V S = V, V V CM = V V CM = V 7 7 TEMPERATURE ( C) 3X G7 OUTPUT SATURATION VOLTAGE (V)... Output Saturation Votage vs Load Current (Output Low) V S = V, V T A = 7 C T A = C T A = C.. LOAD CURRENT (ma) 3X G8 OUTPUT SATURATION VOLTAGE (V)... Output Saturation Votage vs Load Current (Output High) V S = V, V T A = 7 C T A = C T A = C.. LOAD CURRENT (ma) 3X G9 For more information www.inear.com/lt3x 3xf 7
LT3X Typica Performance Characteristics CHANGE IN OFFSET VOLTAGE () 8 8 Minimum Suppy Votage T A = 7 C T A = C T A = C.. 3 3.. TOTAL SUPPLY VOLTAGE (V) 3X G OUTPUT SHORT-CIRCUIT CURRENT (ma) 8 Output Short-Circuit Current vs Power Suppy Votage SOURCING SINKING T A = C T A = 7 C T A = C T A = C 8 T A = 7 C T A = C.. 3 3.. POWER SUPPLY VOLTAGE (±V) 3X G INPUT VOLTAGE ().......... Open-Loop Gain V S = 3V, V R L = Ω.... OUTPUT VOLTAGE (V). 3X G 3. INPUT VOLTAGE (). V S = V, V......... Open-Loop Gain Open-Loop Gain Offset Votage vs Output Current R L = Ω 3 OUTPUT VOLTAGE (V) 3X G3 INPUT VOLTAGE ().......... 3 3 OUTPUT VOLTAGE (V) R L = Ω 3X G OFFSET VOLTAGE () T A = 7 C T A = C T A = C 8 8 OUTPUT CURRENT (ma) 3X G CHANGE IN OFFSET VOLTAGE (µv) 8 Warm-Up Drift vs Time (LT3S8) V S = ±.V V S = ±.V 8 TIME AFTER POWER-UP (s) TOTAL NOISE VOLTAGE (nv/ Hz) Tota Noise vs Tota Source Resistance V S = ±.V V CM = V f = khz TOTAL SPOT NOISE AMPLIFIER SPOT NOISE VOLTAGE RESISTOR SPOT NOISE. k k k TOTAL SOURCE RESISTANCE (Ω) NOISE VOLTAGE (nv Hz) 3 3 Input Noise Votage vs Frequency NPN ACTIVE V CM =.V PNP ACTIVE V CM =.V BOTH ACTIVE V CM =.V V S = V, V k k k 3X G 3X G7 3X G8 8 For more information www.inear.com/lt3x 3xf
Typica Performance Characteristics LT3X BALANCED NOISE CURRENT (pa/ Hz) 7 3 Baanced Noise Current vs Frequency PNP ACTIVE V CM =.V BOTH ACTIVE V CM =.V BALANCED SOURCE RESISTANCE V S = V, V NPN ACTIVE V CM =.V UNBALANCED NOISE CURRENT (pa/ Hz) 8 Unbaanced Noise Current vs Frequency PNP ACTIVE V CM =.V UNBALANCED SOURCE RESISTANCE V S = V, V BOTH ACTIVE V CM =.V NPN ACTIVE V CM =.V OUTPUT VOLTAGE (nv) 8 8.Hz to Hz Output Votage Noise V S = V, V V CM = V S / k k k k k k TIME (s/div) 3X G 3X G9 3X G 3 Gain Bandwidth vs Temperature 9 Phase Margin vs Temperature GAIN BANDWIDTH (MHz) 9 V S = 3V, V PHASE MARGIN (DEG) 8 7 V S = 3V, V 8 7 7 7 TEMPERATURE ( C) 3X G 3 7 7 TEMPERATURE ( C) 3X G3 GAIN () 8 7 3 Open-Loop Gain vs Frequency GAIN PHASE V S = 3V, V 8 V S = 3V, V C L = pf V CM = V 8 k M M M G 3X G PHASE (DEG) GAIN () Open-Loop Gain vs Frequency 8 7 PHASE V CM =.V 8 V CM =.V 3 GAIN V CM =.V V CM =.V V S = V, V C L = pf 8 k M M M G 3X G PHASE (DEG) For more information www.inear.com/lt3x 3xf 9
LT3X Typica Performance Characteristics GAIN BANDWITH (MHz) 8 Gain Bandwidth and Phase Margin vs Suppy Votage C L = pf PHASE MARGIN GAIN BANDWIDTH 8 TOTAL SUPPLY VOLTAGE (V) 3X G 9 8 7 PHASE MARGIN (DEG) SLEW RATE (V/µs) 8 7 3 Sew Rate vs Temperature A V = R F = R G = k RISING FALLING V S = ±.V V S = ±.V 7 7 TEMPERATURE ( C) 3X G7 OUTPUT IMPEDANCE (Ω) Output Impedance vs Frequency VS = V, V A V = A V = A V =.. k M M M 3X G8 COMMON MODE REJECTION RATIO () 8 Common Mode Rejection Ratio vs Frequency V S = V, V V CM = V S / VOLTAGE GAIN () 7 8 9 Chae Separation vs Frequency A V = COMMON MODE REJECTION RATIO () 8 7 3 Power Suppy Rejection Ratio vs Frequency NEGATIVE SUPPLY V S = V, V V CM = V S / POSITIVE SUPPLY k k M M M G. FREQUENCY (MHz) k k k M M M 3X G9 3X G3 3X G3 3 Series Output Resistor vs Capacitive Load V S = V, V A V = 3 Series Output Resistor vs Capacitive Load V S = V, V A V = R S = Ω OVERSHOOT (%) 3 R S = Ω R L = Ω R S = Ω R S = Ω OVERSHOOT (%) 3 R S = Ω R L = Ω R S = Ω CAPACITIVE LOAD (pf) CAPACITIVE LOAD (pf) 3X G3 3X G33 For more information www.inear.com/lt3x 3xf
Typica Performance Characteristics LT3X SETTLING TIME (ns) Setting Time vs Output Step (Noninverting) A V = VIN Ω V OUT 3 3 OUTPUT STEP (V) SETTLING TIME (ns) Setting Time vs Output Step (Inverting) A V = T A = C Ω V IN Ω V OUT 3 3 OUTPUT STEP (V) OUTPUT VOLTAGE SWING (V P-P ) 9 8 7 Maximum Undistorted Output Signa vs Frequency A V = A V = 3 HD, HD 3 < c k k M M 3X G3 3X G3 3X G3 DISTORTION (c) 7 8 9 k Distortion vs Frequency A V = V S = ±.V V OUT = V (P-P) R L = Ω, 3RD R L = Ω, ND, 3RD, ND k M M 3X G37 DISTORTION (c) 7 8 9 k Distortion vs Frequency A V = V OUT = V (P-P) R L = Ω, 3RD R L = Ω, ND, ND, 3RD k M M 3X G38 DISTORTION (c) 7 8 9 k Distortion vs Frequency 3 A V = V S = ±.V V OUT = V (P-P) R L = Ω, 3RD R L = Ω, ND, ND, 3RD k M M 3X G39 DISTORTION (c) 7 8 9 k Distortion vs Frequency A V = V OUT = V (P-P) R L = Ω, ND R L = Ω, 3RD, ND, 3RD k M M 3X G For more information www.inear.com/lt3x 3xf
LT3X Typica Performance Characteristics V Large-Signa Response V Sma-Signa Response V V/DIV /DIV V V V S = V, V A V = ns/div 3X G V S = V, V A V = ns/div 3X G ±V Large-Signa Response Output-Overdrive Recovery V V/DIV V V IN (V/DIV) V V V OUT (V/DIV) V A V = ns/div 3X G3 V S = V, V A V = ns/div 3X G Pin Functions OUT A (Pin ): Ampifier A Output. The output swings rai-to-rai and can source/sink a minimum of ma over temperature. IN A (Pin ): Inverting Input of Ampifier A. Vaid input range is from V to V. IN A (Pin 3): Non-Inverting Input of Ampifier A. Vaid input range is from V to V. V (Pin ): Negative Suppy Votage. V and V must be chosen so that 3V (V V ) <.V. IN B (Pin ): Non-Inverting Input of Ampifier B. Vaid input range from V to V. IN B (Pin ): Inverting Input of Ampifier B. Vaid input range from V to V. OUT B (Pin 7): Ampifier B Output. The output swings rai-to-rai and can source/sink a minimum of ma over temperature. V (Pin 8): Positive Suppy Votage. V and V must be chosen so that 3V (V V ) <.V. For more information www.inear.com/lt3x 3xf
LT3X Appications Information Ampifier Characteristics Figure shows a simpified schematic of the LT3X, which has two input differentia ampifiers in parae that are biased on simutaneousy when the common mode votage is at east.v from either rai. This topoogy aows the input stage to swing from the positive suppy votage to the negative suppy votage. As the common mode votage swings beyond V CC.V, current source I saturates and current in Q/Q is zero. Feedback is maintained through the Q/Q3 differentia ampifier, but with an input g m reduction of /. A simiar effect occurs with I when the common mode votage swings within.v of the negative rai. The effect of the g m reduction is a shift in the V OS as I or I saturate. Input bias current normay fows out of the and inputs. The magnitude of this current increases when the input common mode votage is within.v of the negative rai, and ony Q/Q are active. The poarity of this current reverses when the input common mode votage is within.v of the positive rai and ony Q/Q3 are active. The second stage is a foded cascode and current mirror that converts the input stage differentia signas to a singe ended output. Capacitor C reduces the unity cross frequency and improves the frequency stabiity without degrading the gain bandwidth of the ampifier. The differentia drive generator suppies current to the output transistors that swing from rai-to-rai. R I R V BIAS V Q V DESD DESD3 V DESD D DESD D Q Q Q3 Q Q Q8 C V Q9 Q7 Q C M DIFFERENTIAL DRIVE GENERATOR V DESD DESD V V Q V R3 R R I D3 V 3X F Figure. Simpified Schematic For more information www.inear.com/lt3x 3xf 3
LT3X Appications Information Input Protection There are back-to-back diodes, D and D, across the and inputs of these ampifiers to imit the differentia input votage to ±.7V. The inputs of the LT3X do not have interna resistors in series with the input transistors. This technique is often used to protect the input devices from over votage that causes excessive currents to fow. The addition of these resistors woud significanty degrade the ow noise votage of these ampifiers. For instance, a Ω resistor in series with each input woud generate.8nv/ Hz of noise, and the tota ampifier noise votage woud rise from.9nv/ Hz to.nv/ Hz. Once the input differentia votage exceeds ±.7V, steady state current conducted though the protection diodes shoud be imited to ±ma. This impies Ω of protection resistance per vot of continuous overdrive beyond ±.7V. The input diodes are rugged enough to hande transient currents due to ampifier sew rate overdrive or momentary cipping without these resistors. Figure shows the input and output waveforms of the ampifier driven into cipping whie coected in a gain of A V =. When the input signa goes sufficienty beyond the power suppy rais, the input transistors wi saturate. When saturation occurs, the ampifier oses a stage of phase inversion and the output tries to change states. Diodes D and D forward bias and hod the output within OV Figure. V S = ±.V, A V = with Large Overdrive a diode drop of the input signa. In this photo, the input signa generator is cipping at ±3mA, and the output transistors suppy this generator current through the protection diodes. With the ampifier coected in a gain of A V, the output can invert with very heavy input overdrive. To avoid this inversion, imit the input overdrive to.v beyond the power suppy rais. ESD The LT3X has reverse-biased ESD protection diodes on a inputs and outputs as shown in Figure. If these pins are forced beyond either suppy, unimited current wi fow through these diodes. If the current is transient and imited to one hundred miiamps or ess, no damage to the device wi occur. Noise The noise votage of the LT3X is equiva ent to that of a Ω resistor, and for the owest possibe noise it is desirabe to keep the source and feedback resistance at or beow this vaue, i.e. R S R G R FB Ω. With R S R G R FB = Ω the tota noise of the ampifier is: e n = (.9nV) (.9nV) =.7nV. Beow this resistance vaue, the ampifier dominates the noise, but in the resistance region between Ω and approximatey kω, the noise is dominated by the resistor therma noise. As the tota resistance is further increased, beyond k, the noise current mutipied by the tota resistance eventuay dominates the noise. The product of e n I SUPPLY is an interesting way to gauge ow noise ampifiers. Many ow noise ampifiers with ow e n have high I SUPPLY current. In appications that require ow noise with the owest possibe suppy current, this product can prove to be enightening. The LT3X has an e n, I SUPPLY product of 3. per ampifier, yet it is common to see ampifiers with simiar noise specifications have an e n I SUPPLY product of.7 to 3.. For a compete discussion of ampifier noise, see the LT8 data sheet. For more information www.inear.com/lt3x 3xf
Package Description Pease refer to http://www.inear.com/product/lt3x#packaging for the most recent package drawings. LT3X S8 Package 8-Lead Pastic Sma Outine (Narrow. Inch) (Reference LTC DWG # -8- Rev G). BSC. ±..89.97 (.8.) NOTE 3 8 7. MIN. ±..8. (.79.97)..7 (3.8 3.988) NOTE 3.3 ±. TYP RECOMMENDED SOLDER PAD LAYOUT 3.8. (.3.).. (..8) 8 TYP.3.9 (.3.7).. (..).. (..7) NOTE: INCHES. DIMENSIONS IN (MILLIMETERS)..9 (.3.83) TYP. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED." (.mm). PIN CAN BE BEVEL EDGE OR A DIMPLE. (.7) BSC SO8 REV G Information furnished by Linear Technoogy Corporation is beieved to be accurate and reiabe. However, no responsibiity is assumed for its use. Linear Technoogy Corporation makes no representation that the intercoection For more of its circuits information as described www.inear.com/lt3x herein wi not infringe on existing patent rights. 3xf
LT3X Typica Appication Low Noise Differentia Ampifier with Gain Adjust and Common Mode Contro V IN V IN R Ω R Ω R3 Ω R Ω R Ω R Ω C 7pF R7, Ω V / LT3X R8 Ω V R A C pf R9 Ω R B.µF / LT3X C3 pf R, Ω V OUT V OUT ( ) R OUTPUT V B CM = V R A R B LT3X TAa Low Noise Differentia Ampifier Frequency Response RELATIVE DIFFERENTIAL GAIN (/DIV) G = G = G = k M LT3X TAb M Reated Parts PART NUMBER DESCRIPTION COMMENTS LT8 Singe, Utraow Noise MHz Op Amp.8nV/ Hz LT77 Singe, Low Noise Rai-to-Rai Ampifier 3V Operation,.mA,.nV/ Hz, µv Max V S LT7/LT73/LT7 Singe/Dua/Quad Low Noise Precision Op Amps 7V/µs Sew Rate, µv Max V OS, 3.8nV/ Hz, 3.7mA LT8/LT8/LT8 Singe/Dua/Quad Low Power 8MHz Rai-to-Rai Op Amps 8.nV/ Hz, ma Max Suppy LT8/LT87 Singe/Dua, Low Noise 3MHz Rai-to-Rai Ampifiers.V Operation, µv Max V OS, 3.nV/ Hz LT Singe Utraow Noise Rai-to-Rai Ampifier.9nV/ Hz, MHz Gain Bandwidth 3xf LT 7 PRINTED IN USA www.inear.com/lt3x For more information www.inear.com/lt3x LINEAR TECHNOLOGY CORPORATION 7