- PDF Free Download

Size: px

Start display at page:

Download ""

Coleen Stone
5 years ago
Views:

1 Distributed by: The content and copyrights of the attached material are the property of its owner.

2 FEATRES Input Bias Current, Warmed p: pa Max % Tested Low Voltage Noise: 8nV/ Hz Max A Grade % Temperature Tested Offset Voltage Over Temp: mv Max Input Resistance: Ω Very Low Input Capacitance:.pF Voltage Gain: Million Min Gain-Bandwidth Product:.2MHz Typ Guaranteed Specifications with ±V Supplies APPLICATIO S Photocurrent Amplifiers Hydrophone Amplifiers High Sensitivity Piezoelectric Accelerometers Low Voltage and Current Noise Instrumentation Amplifier Front Ends Two and Three Op Amp Instrumentation Amplifiers Active Filters, LTC and LT are registered trademarks of Linear Technology Corporation. LT9 Low Noise, Picoampere Bias Current, JFET Input Op Amp DESCRIPTIO The LT 9 achieves a new standard of excellence in noise performance for a JFET op amp. For the first time low voltage noise (nv/ Hz) is simultaneously offered with extremely low current noise (.8fA/ Hz), providing the lowest total noise for high impedance transducer applications. nlike most JFET op amps, the very low input bias current (pa typ) is maintained over the entire common mode range which results in an extremely high input resistance ( Ω). When combined with a very low input capacitance (.pf) an extremely high input impedance results, making the LT9 the first choice for amplifying low level signals from high impedance transducers. The low input capacitance also assures high gain linearity when buffering AC signals from high impedance transducers. The LT9 is unconditionally stable for gains of or more, even with pf capacitive loads. Other key features are 2µV V OS and a voltage gain over million. Each individual amplifier is % tested for voltage noise, slew rate (.V/µs) and gain-bandwidth product (.2MHz). Specifications at ±V supply operation are also provided. For an even lower voltage noise please see the LT92 data sheet. TYPICAL APPLICATIO Low Noise Light Sensor with DC Servo C 2pF khz Output Voltage Noise Density vs Source Resistance HAMAMATS S-BK (98) 2-9 D2 N9 C D 2N9 V R k 2 R k D N9 V LT9 V R k R2C2 > CR V LT9 V R M C2.22µF 9 TA C D = PARASITIC PHOTODIODE CAPACITANCE V OT = mv/µwatt FOR 2nm WAVE LENGTH mv/µwatt FOR nm WAVE LENGTH R2 k V OT TOTAL khz VOLTAGE NOISE DENSITY (nv/ Hz) k k R SORCE V N V N SORCE RESISTANCE ONLY k k k M M M G SORCE RESISTANCE (Ω) V N = (V OP AMP ) 2 ktr S 2qI B R 2 S 9 TA2

3 LT9 ABSOLTE AXI RATI GS (Note ) W W W Supply Voltage... ±2V Differential Input Voltage... ±V Input Voltage (Equal to Supply Voltage)... ±2V Output Short-Circuit Duration... Indefinite Operating Temperature Range... C to 8 C Specified Temperature Range Commercial (Note 8)... C to 8 C Industrial... C to 8 C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... C PACKAGE/ORDER I FOR V OS ADJ IN A IN A V 2 TOP VIEW N8 PACKAGE 8-LEAD PDIP 8 T JMAX = C, θ JA = 8 C/W Consult factory for Military grade parts. A NC V OT V OS ADJ W ATIO ORDER PART NMBER LT9ACN8 LT9CN8 LT9AIN8 LT9IN8 V OS ADJ IN A 2 IN A V TOP VIEW A 8 S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = C, θ JA = 9 C/W NC V OT V OS ADJ ORDER PART NMBER LT9ACS8 LT9CS8 LT9AIS8 LT9IS8 S8 PART MARKING 9A 9 9AI 9I ELECTRICAL CHARACTERISTICS,, V CM = V, unless otherwise noted. LT9AC/LT9AI LT9C/LT9I SYMBOL PARAMETER CONDITIONS (Note 2) MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage mv V S = ±V.... mv I OS Input Offset Current Warmed p (Note ). 2. pa T J = 2 C (Note ). 2. pa I B Input Bias Current Warmed p (Note ). 2 pa T J = 2 C (Note ). pa e n Input Noise Voltage.Hz to Hz µv P-P Input Noise Voltage Density f O = Hz.. nv/ Hz f O = Hz 8 8 nv/ Hz i n Input Noise Current Density f O = Hz, f O = khz (Note ).8 fa/ Hz R IN Input Resistance Differential Mode Ω Common Mode V CM = V to V Ω C IN Input Capacitance.. pf V S = ±V pf V CM Input Voltage Range (Note ).... V.... V CMRR Common Mode Rejection Ratio V CM = V to V db PSRR Power Supply Rejection Ratio V S = ±.V to ± 2V db 2

4 ELECTRICAL CHARACTERISTICS,, V CM = V, unless otherwise noted. LT9 LT9AC/LT9AI LT9C/LT9I SYMBOL PARAMETER CONDITIONS (Note 2) MIN TYP MAX MIN TYP MAX NITS A VOL Large-Signal Voltage Gain V O = ±2V, R L = k 9 V/mV V O = ±V, R L = k V/mV V OT Output Voltage Swing R L = k ±. ±.2 ±. ±.2 V R L = k ±2. ±2. ±2. ±2. V SR Slew Rate R L 2k (Note ) V/µs GBW Gain-Bandwidth Product f O = khz MHz I S Supply Current ma V S = ±V ma Offset Voltage R POT (to V EE ) = k mv Adjustment Range The denotes specifications which apply over the temperature range C T A C, otherwise specifications are at., V CM = V, unless otherwise noted. (Note 9) LT9AC LT9C SYMBOL PARAMETER CONDITIONS (Note 2) MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage.... mv V S = ±V....2 mv V OS Average Input Offset (Note ) 8 µv/ C Temp Voltage Drift I OS Input Offset Current 2 pa I B Input Bias Current pa V CM Input Voltage Range (Note ) V V CMRR Common Mode Rejection Ratio V CM = V to 2.9V 9 9 db PSRR Power Supply Rejection Ratio V S = ±.V to ± 2V db A VOL Large-Signal Voltage Gain V O = ±2V, R L = k 9 8 V/mV V O = ±V, R L = k 2 2 V/mV V OT Output Voltage Swing R L = k ±2.9 ±.2 ±2.9 ±.2 V R L = k ±.9 ±2. ±.9 ±2. V SR Slew Rate R L 2k (Note ) V/µs GBW Gain-Bandwidth Product f O = khz MHz I S Supply Current ma V S = ±V ma

5 LT9 ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the temperature range C T A 8 C., V CM = V, unless otherwise noted. (Notes 8, 9) LT9AC/LT9AI LT9C/LT9I SYMBOL PARAMETER CONDITIONS (Note 2) MIN TYP MAX MIN TYP MAX NITS V OS Input Offset Voltage....8 mv V S = ±V mv V OS Average Input Offset (Note ) 9 µv/ C Temp Voltage Drift I OS Input Offset Current 8 pa I B Input Bias Current 2 8 pa V CM Input Voltage Range (Note ) V.... V CMRR Common Mode Rejection Ratio V CM = V to 2.V db PSRR Power Supply Rejection Ratio V S = ±.V to ± 2V db A VOL Large-Signal Voltage Gain V O = ±2V, R L = k 8 V/mV V O = ±V, R L = k 22 2 V/mV V OT Output Voltage Swing R L = k ±2.8 ±. ±2.8 ±. V R L = k ±.8 ±2. ±.8 ±2. V SR Slew Rate R L 2k V/µs GBW Gain-Bandwidth Product f O = khz MHz I S Supply Current ma V S = ±V ma Note : Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Typical parameters are defined as the % yield of parameter distributions of individual amplifiers. Note : I B and I OS readings are extrapolated to a warmed-up temperature from 2 C measurements and 2 C characterization data. Note : Current noise is calculated from the formula: i n = (2qI B ) /2 where q =. 9 coulomb. The noise of source resistors up to 2M swamps the contribution of current noise. Note : Input voltage range functionality is assured by testing offset voltage at the input voltage range limits to a maximum of 2.mV (A grade) to 2.8mV (C grade). Note : This parameter is not % tested. Note : Slew rate is measured in A V = ; input signal is ±.V, output measured at ±2.V. Note 8: The LT9AC and LT9C are guaranteed to meet specified performance from C to C and are designed, characterized and expected to meet these extended temperature limits, but are not tested at C and 8 C. The LT9I is guaranteed to meet the extended temperature limits. The LT9AC and LT9AI grade are % temperature tested for the specified temperature range. Note 9: The LT9 is measured in an automated tester in less than one second after application of power. Depending on the package used, power dissipation, heat sinking, and air flow conditions, the fully warmed-up chip temperature can be C to C higher than the ambient temperature.

6 LT9 TYPICAL PERFOR A W CE CHARACTERISTICS VOLTAGE NOISE (µv/div).hz to Hz Voltage Noise PERCENT OF NITS (%) 2 khz Input Noise Voltage Distribution OP AMPS TESTED RMS VOLTAGE NOISE DENSITY (nv/ Hz) Voltage Noise vs Frequency /f CORNER Hz 2 8 TIME (SEC) INPT VOLTAGE NOISE (nv/ Hz) k k FREQENCY (Hz) 9 G 9 G2 9 G VOLTAGE NOISE (AT khz) (nv/ Hz) 9 8 Voltage Noise vs Chip Temperature TEMPERATRE ( C) 9 G COMMON MODE LIMIT (V) REFERRED TO POWER SPPLY V V 2. Common Mode Limit vs Temperature V = V TO 2V 2 2 TEMPERATRE ( C) V = V TO 2V 9 G COMMON MODE REJECTION RATIO (db) Common Mode Rejection Ratio vs Frequency k k k M M FREQENCY (Hz) 9 G POWER SPPLY REJECTION RATIO (db) Power Supply Rejection Ratio vs Frequency PSRR PSRR k k k FREQENCY (Hz) M M VOLTAGE GAIN (db) Voltage Gain vs Frequency C L = pf k M M FREQENCY (Hz) VOLTAGE GAIN (db) 2. Gain and Phase Shift vs Frequency GAIN PHASE C L = pf FREQENCY (MHz) PHASE SHIFT (DEG) 9 G 9 G8 9 G9

LT9 TYPICAL PERFOR 2mV/DIV Small-Signal Transient Response A V = C L = pf, ±V µs/div A W 9 G CE CHARACTERISTICS V/DIV Large-Signal Transient Response A V = C L = pf R L = 2k µs/div 9 G V.8.

R L k V O = mv P-P A V = R F = k C F = 2pF A V = A V = CAPACITIVE LOAD (pf) CHANGE IN OFFSET VOLTAGE (µv) 9 Warm-p Drift SO-8 PACKAGE N8 PACKAGE 2 TIME AFTER POWER ON (MINTES) TOTAL HARMONIC

7 LT9 TYPICAL PERFOR 2mV/DIV Small-Signal Transient Response A V = C L = pf, ±V µs/div A W 9 G CE CHARACTERISTICS V/DIV Large-Signal Transient Response A V = C L = pf R L = 2k µs/div 9 G V OTPT VOLTAGE SWING (V) Output Voltage Swing vs Load Current 2 C C V S = ±V TO ±2V 2 C C 2 C 2 C V I SINK I OTPT CRRENT (ma) SORCE 9 G2 OVERSHOOT (%) 2 Capacitive Load Handling. R L k V O = mv P-P A V = R F = k C F = 2pF A V = A V = CAPACITIVE LOAD (pf) CHANGE IN OFFSET VOLTAGE (µv) 9 Warm-p Drift SO-8 PACKAGE N8 PACKAGE 2 TIME AFTER POWER ON (MINTES) TOTAL HARMONIC DISTORTION NOISE (%)... THD and Noise Frequency for Noninverting Gain Z L = 2k pf V O = 2VP-P A V =,, MEASREMENT BANDWIDTH = Hz TO 8kHz. 2 A V = A V = A V = NOISE FLOOR k FREQENCY (Hz) k 2k 9 G 9 G 9 G TOTAL HARMONIC DISTORTION NOISE (%)... THD and Noise vs Frequency for Inverting Gain Z L = 2k pf V O = 2VP-P A V =,, MEASREMENT BANDWIDTH = Hz TO 8kHz. 2 NOISE FLOOR A V = A V = k FREQENCY (Hz) A V = k 2k 9 G TOTAL HARMONIC DISTORTION NOISE (%)..... THD and Noise vs Output Amplitude for Inverting Gain Z L = 2k pf, f O = khz A V =,, MEASREMENT BANDWIDTH = Hz TO 22kHz A V = A V = A V = OTPT SWING (V P-P ) 9 G TOTAL HARMONIC DISTORTION NOISE (%)..... THD and Noise vs Output Amplitude for Noninverting Gain Z L = 2k pf, f O = khz A V =,, MEASREMENT BANDWIDTH = Hz TO 22kHz A V = A V = A V = OTPT SWING (V P-P ) 9 G8

8 LT9 TYPICAL PERFOR A W CE CHARACTERISTICS OTPT CRRENT (ma) 2 2 Short-Circuit Output Current vs Temperature SINK SORCE SPPLY CRRENT PER AMPLIFIER (ma) Supply Current vs Temperature V S = ±V INPT BIAS AND OFFSET CRRENTS (A) n n n n p p p p p p Input Bias and Offset Currents vs Chip Temperature V CM = TO V BIAS CRRENT OFFSET CRRENT TEMPERATRE ( C) TEMPERATRE ( C).p 2 2 TEMPERATRE ( C) 9 G9 9 G2 9 G2 APPLICATI O S LT9 vs the Competition I FOR W ATIO With improved noise performance, the LT9 in the PDIP directly replaces such JFET op amps as the OPA and the AD. The combination of low current and voltage noise of the LT9 allows it to surpass most dual and single JFET op amps. The LT9 can replace many of the lowest noise bipolar amps that are used in amplifying low level signals from high impedance transducers. The best bipolar op amps (with higher current noise) will eventually lose out to the LT9 when transducer impedance increases. INPT BIAS CRRENT (pa) CRRENT NOISE = 2qI B AD822 OP2 LT9 COMMON MODE RANGE (V) 9 F Figure. Comparison of LT9, OP2, and AD822 Input Bias Current vs Common Mode Range The extremely high input impedance ( Ω) assures that the input bias current is almost constant over the entire common mode range. Figure shows how the LT9 stands up to the competition. nlike the competition, as the input voltage is swept across the entire common mode range the input bias current of the LT9 hardly changes. As a result the current noise does not degrade. This makes the LT9 the best choice in applications where an amplifier has to buffer signals from a high impedance transducer. Offset nulling will be compatible with these devices with the wiper of the potentiometer tied to the negative supply (Figure 2a). No appreciable change in offset voltage drift 2 V (a) k V V OS = ±mv Figure 2 2 k V (b) k k V V OS = ±.mv 9 F2

9 LT9 APPLICATI O S I FOR W ATIO with temperature will occur when the device is nulled with a potentiometer ranging from k to 2k. Finer adjustments can be made with resistors in series with the potentiometer (Figure 2b). Amplifying Signals from High Impedance Transducers The low voltage and current noise offered by the LT9 makes it useful in a wide range of applications, especially where high impedance, capacitive transducers are used such as hydrophones, precision accelerometers and photodiodes. The total output noise in such a system is the gain times the RMS sum of the op amp s input referred INPT NOISE VOLTAGE (nv/ H z) k k R S C S R S C S LT9 V O LT* LT9* LT9 LT RESISTOR NOISE ONLY LT k k k M M M G SORCE RESISTANCE (Ω) SORCE RESISTANCE = 2R S = R * PLS RESISTOR PLS RESISTOR pf CAPACITOR V n = A V V n 2 (OP AMP) ktr 2qI B R 2 9 F Figure. Comparison of LT9 and LT Total Output khz Voltage Noise vs Source Resistance voltage noise, the thermal noise of the transducer, and the op amp s input bias current noise times the transducer impedance. Figure shows total input voltage noise versus source resistance. In a low source resistance (<k) application the op amp voltage noise will dominate the total noise. This means the LT9 is superior to most JFET op amps. Only the lowest noise bipolar op amps have the advantage at low source resistances. As the source resistance increases from k to k, the LT9 will match the best bipolar op amps for noise performance, since the thermal noise of the transducer (ktr) begins to dominate the total noise. A further increase in source resistance, above k, is where the op amp s current noise component (2qI B R 2 ) will eventually dominate the total noise. At these high source resistances, the LT9 will out perform the lowest noise bipolar op amps due to the inherently low current noise of FET input op amps. Clearly, the LT9 will extend the range of high impedance transducers that can be used for high signal-to-noise ratios. This makes the LT9 the best choice for high impedance, capacitive transducers. Optimization Techniques for Charge Amplifiers The high input impedance JFET front end makes the LT9 suitable in applications where very high charge sensitivity is required. Figure illustrates the LT9 in its inverting and noninverting modes of operation. A charge amplifier is shown in the inverting mode example; the gain depends on the principal of charge conservation at the input of the LT9. The charge across the transducer capacitance C S is transferred to the feedback capacitor C F R F C F C B R2 R B C S R S OTPT R OTPT TRANSDCER C B R B C B = C F C S R B = R F R S dq dv Q = CV; = I = C dt dt C S R S CB C S R B = R S R S > R OR R2 TRANSDCER 9 F 8 Figure. Inverting and Noninverting Gain Configurations

In the noninverting mode example, the transducer current is converted to a change in voltage by the transducer capacitance, C S. This voltage is then buffered by the LT9 with a gain of R/R2.

10 LT9 APPLICATI O S I FOR W ATIO resulting in a change in voltage dv, which is equal to dq/c F. The gain therefore is C F /C S. For unity-gain, the C F should equal the transducer capacitance plus the input capacitance of the LT9 and R F should equal R S. In the noninverting mode example, the transducer current is converted to a change in voltage by the transducer capacitance, C S. This voltage is then buffered by the LT9 with a gain of R/R2. A DC path is provided by R S, which is either the transducer impedance or an external resistor. Since R S is usually several orders of magnitude greater than the parallel combination of R and R2, R B is added to balance the DC offset caused by the noninverting input bias current and R S. The input bias currents, although small at room temperature, can create significant errors at higher temperature, especially with transducer resistances of up to M or more. The optimum value for R B is determined by equating the thermal noise (ktr S ) to the current noise (2qI B ) times R S 2. Solving for R S results in R B = R S = 2V T /I B (V T = 2mV at 2 C). A parallel capacitor C B, is used to cancel the phase shift caused by the op amp input capacitance and R B. Reduced Power Supply Operation To take full advantage of a wide input common mode range, the LT9 was designed to eliminate phase reversal. Referring to the photographs in Figure, the LT9 is shown operating in the follower mode (A V = ) at ±V supplies with the input swinging ±.2V. The output of the LT9 clips cleanly and recovers with no phase reversal. This has the benefit of preventing lockup in servo systems and minimizing distortion components. Input: ±.2V Sine Wave LT9 Output LT9 Fa LT9 Fb Figure. Voltage Follower with Input Exceeding the Common Mode Range (V S = ±V) 9

11 LT9 PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow.) (LTC DWG # -8-).* (.) MAX 8.2 ±.* (. ±.8) 2..2 (.2 8.2).. (..). ±. (.2 ±.2).9. (.229.8) ( ). (.) TYP. ±. (2. ±.2) *THESE DIMENSIONS DO NOT INCLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. INCH (.2mm).2 (.) MIN.8 ±. (. ±.).2 (.8) MIN N8 9

12 LT9 PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow.) (LTC DWG # -8-).89.9* (.8.) (.9.9)..** (.8.988) 2.8. (.2.2)..2 (.2.8) 8 TYP..9 (..2).. (..2)....2 * DIMENSION DOES NOT INCLDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED." (.2mm) PER SIDE ** DIMENSION DOES NOT INCLDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED." (.2mm) PER SIDE..9 (..8). (.2) TYP SO8 99 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.

13 LT9 TYPICAL APPLICATIONS N Hz Fourth Order Chebyshev Lowpass Filter (.db Ripple) R2 2k R k V IN R 2k C2 nf R 29k V 2 LT9 V C nf R k R 29k C nf 2 C nf LT9 V OT 9 TA TYPICAL OFFSET.8mV % TOLERANCES FOR V IN = V P-P, V OT = 2dB AT f > Hz = db AT f =.Hz LOWER RESISTOR VALES WILL RESLT IN LOWER THERMAL NOISE AND LARGER CAPACITORS Accelerometer Amplifier with DC Servo C 2pF R M R2 8k R 2k C2 2µF ACCELEROMETER B & K MODEL 8 OR EQIVALENT (8) 2-2 R 2M /2 LT R 2M V TO V C 2 2µF LT9 OTPT 9 TA RC2 = RC > R ( R2/R) C OTPT =.8mV/pC* = 8.mV/g** V TO V DC OTPT.9mV OTPT NOISE = 8nV/ H z AT khz *PICOCOLOMBS **g = EARTH S GRAVITATIONAL CONSTANT RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT Low Noise, Dual JFET Op Amp Dual Version of LT92, V NOISE =.nv/ Hz LT9 Low Noise, Dual JFET Op Amp Dual Version of LT9, V NOISE = nv/ Hz, I B = pa LT Micropower Dual JFET Op Amp MHz, 2pA Max I B, 2µA Max I S LT92 Low Noise, Single JFET Op Amp Lower V NOISE Version of LT9, V NOISE =.2nV/ Hz 2 9f LT/TP 99 K PRINTED IN SA Linear Technology Corporation McCarthy Blvd., Milpitas, CA 9- (8) 2-9 FAX: (8) - LINEAR TECHNOLOGY CORPORATION 999

LT1169 Dual Low Noise, Picoampere Bias Current, JFET Input Op Amp DESCRIPTIO U S

LT1169 Dual Low Noise, Picoampere Bias Current, JFET Input Op Amp DESCRIPTIO U S FEATRES Input Bias Current, Warmed p: pa Max % Tested Low Voltage Noise: nv/ Hz Max S and N Package Standard Pinout Very Low Input Capacitance:.pF Voltage Gain:. Million Min Offset Voltage: mv Max Input