LT1793 Low Noise, Picoampere Bias Current, JFET Input Op Amp U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®1793 achieves a new standard of excellence in noise performance for a JFET op amp. For the first time low voltage noise (6nV/√Hz) is simultaneously offered with extremely low current noise (0.8fA/√Hz), providing the lowest total noise for high impedance transducer applications. Unlike most JFET op amps, the very low input bias current (3pA typ) is maintained over the entire common mode range which results in an extremely high input resistance (1013Ω). When combined with a very low input capacitance (1.5pF) an extremely high input impedance results, making the LT1793 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. Input Bias Current, Warmed Up: 10pA Max 100% Tested Low Voltage Noise: 8nV/√Hz Max A Grade 100% Temperature Tested Offset Voltage Over Temp: 1mV Max Input Resistance: 1013Ω Very Low Input Capacitance: 1.5pF Voltage Gain: 1 Million Min Gain-Bandwidth Product: 4.2MHz Typ Guaranteed Specifications with ±5V Supplies U 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 The LT1793 is unconditionally stable for gains of 1 or more, even with 1000pF capacitive loads. Other key features are 250µV VOS and a voltage gain over 4 million. Each individual amplifier is 100% tested for voltage noise, slew rate (3.4V/µs) and gain-bandwidth product (4.2MHz). Specifications at ±5V supply operation are also provided. For an even lower voltage noise please see the LT1792 data sheet. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Low Noise Light Sensor with DC Servo 1kHz Output Voltage Noise Density vs Source Resistance V+ – 2 + 3 D2 1N914 R1 1M 7 LT1793 6 VOUT C2 0.022µF 4 CD D1 1N914 2N3904 LT1097 R5 10k V– R3 1k R2 100k R4 1k + HAMAMATSU S1336-5BK (908) 231-0960 V+ – V– 1793 TA01 V– R2C2 > C1R1 CD = PARASITIC PHOTODIODE CAPACITANCE VOUT = 100mV/µWATT FOR 200nm WAVE LENGTH 330mV/µWATT FOR 633nm WAVE LENGTH TOTAL 1kHz VOLTAGE NOISE DENSITY (nV/√Hz) C1 2pF 10k – 1k VN + RSOURCE 100 10 1 100 VN SOURCE RESISTANCE ONLY 1k TA = 25°C VS = ±15V 10k 100k 1M 10M 100M 1G SOURCE RESISTANCE (Ω) VN = √(VOP AMP)2 + 4kTRS + 2qIBRS2 1793 TA02 1 LT1793 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage ..................................................... ±20V Differential Input Voltage ...................................... ±40V Input Voltage (Equal to Supply Voltage) ............... ±20V Output Short-Circuit Duration ........................ Indefinite Operating Temperature Range ............... – 40°C to 85°C Specified Temperature Range Commercial (Note 8) ......................... – 40°C to 85°C Industrial ........................................... – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec) ................ 300°C W U U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW VOS ADJ 1 8 NC – IN A 2 + + IN A 3 V – A 7 V 6 OUT 5 VOS ADJ 4 LT1793ACN8 LT1793CN8 LT1793AIN8 LT1793IN8 ORDER PART NUMBER TOP VIEW VOS ADJ 1 8 NC –IN A 2 7 V+ +IN A 3 A LT1793ACS8 LT1793CS8 LT1793AIS8 LT1793IS8 6 OUT V– 4 5 VOS ADJ N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 80°C/W TJMAX = 160°C, θJA = 190°C/W S8 PART MARKING 1793AI 1793I 1793A 1793 Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS TA = 25°C, VS = ±15V, VCM = 0V, unless otherwise noted. LT1793AC/LT1793AI MIN TYP MAX LT1793C/LT1793I MIN TYP MAX VS = ±5V 0.25 0.45 0.8 1.4 0.25 0.45 0.9 1.6 mV mV Input Offset Current Warmed Up (Note 3) TJ = 25°C (Note 6) 1.5 0.5 7 2 2.5 0.7 15 4 pA pA IB Input Bias Current Warmed Up (Note 3) TJ = 25°C (Note 6) 3 1 10 3 4.0 1.5 20 5 pA pA en Input Noise Voltage 0.1Hz to 10Hz 2.4 2.4 µVP-P Input Noise Voltage Density fO = 10Hz fO = 1000Hz 11.5 6 8 11.5 6 8 nV/√Hz nV/√Hz fO = 10Hz, fO = 1kHz (Note 4) 0.8 1 VCM = –10V to 13V 1014 1013 1014 1013 Ω Ω VS = ±5V 1.5 2.0 1.5 2.0 pF pF SYMBOL PARAMETER VOS Input Offset Voltage IOS in Input Noise Current Density RIN Input Resistance Differential Mode Common Mode CIN Input Capacitance VCM Input Voltage Range (Note 5) CMRR Common Mode Rejection Ratio PSRR Power Supply Rejection Ratio 2 CONDITIONS (Note 2) UNITS fA/√Hz 13.0 – 10.5 13.5 – 11.0 13.0 – 10.5 13.5 – 11.0 V V VCM = –10V to 13V 83 102 81 96 dB VS = ±4.5V to ± 20V 85 98 83 95 dB LT1793 ELECTRICAL CHARACTERISTICS TA = 25°C, VS = ±15V, VCM = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS (Note 2) LT1793AC/LT1793AI MIN TYP MAX LT1793C/LT1793I MIN TYP MAX AVOL Large-Signal Voltage Gain VO = ±12V, RL = 10k VO = ±10V, RL = 1k 1000 500 4500 3500 900 400 4400 3000 V/mV V/mV VOUT Output Voltage Swing RL = 10k RL = 1k ±13.0 ±12.0 ±13.2 ±12.3 ±13.0 ±12.0 ±13.2 ±12.3 V V SR Slew Rate RL ≥ 2k (Note 7) 2.3 3.4 2.3 3.4 GBW Gain-Bandwidth Product fO = 100kHz 2.5 4.2 2.5 4.2 IS Supply Current Offset Voltage Adjustment Range VS = ±5V 4.2 4.2 RPOT (to VEE) = 10k 13 5.20 5.15 4.2 4.2 UNITS V/µs MHz 5.20 5.15 13 mA mA mV The ● denotes specifications which apply over the temperature range 0°C ≤ TA ≤ 70°C, otherwise specifications are at TA = 25°C. VS = ±15V, VCM = 0V, unless otherwise noted. (Note 9) SYMBOL PARAMETER VOS Input Offset Voltage ∆VOS ∆Temp Average Input Offset Voltage Drift IOS CONDITIONS (Note 2) MIN LT1793AC TYP MAX MIN LT1793C TYP MAX UNITS VS = ±5V ● ● 0.50 0.75 1.0 1.6 1.0 1.6 3.5 4.2 mV mV (Note 6) ● 5 13 8 50 µV/°C Input Offset Current ● 15 100 20 130 pA IB Input Bias Current ● 130 400 150 500 pA VCM Input Voltage Range (Note 5) ● ● 12.9 – 10.0 13.4 – 10.8 CMRR Common Mode Rejection Ratio VCM = –10V to 12.9V ● 79 100 77 95 dB PSRR Power Supply Rejection Ratio VS = ±4.5V to ± 20V ● 83 97 81 94 dB AVOL Large-Signal Voltage Gain VO = ±12V, RL = 10k VO = ±10V, RL = 1k ● ● 900 500 3600 2600 800 400 3400 2400 VOUT Output Voltage Swing RL = 10k RL = 1k ● ● SR Slew Rate RL ≥ 2k (Note 7) ● 2.2 3.3 GBW Gain-Bandwidth Product fO = 100kHz ● 2.2 3.3 IS Supply Current VS = ±5V ● ● 12.9 – 10.0 ±12.9 ±13.2 ±11.9 ±12.15 4.2 4.2 13.4 – 10.8 V V V/mV V/mV ±12.9 ±13.2 ±11.9 ±12.15 5.30 5.25 2.2 3.3 2.2 3.3 4.2 4.2 V V V/µs MHz 5.30 5.25 mA mA 3 LT1793 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the temperature range – 40°C ≤ TA ≤ 85°C. VS = ±15V, VCM = 0V, unless otherwise noted. (Notes 8, 9) LT1793AC/LT1793AI MIN TYP MAX LT1793C/LT1793I MIN TYP MAX VS = ±5V ● ● 0.65 1.00 1.3 1.9 1.6 2.0 4.8 5.5 mV mV (Note 6) ● 5 13 9 50 µV/°C Input Offset Current ● 80 300 100 400 pA IB Input Bias Current ● 700 2400 800 3000 pA VCM Input Voltage Range (Note 5) ● ● 12.6 – 10.0 13.0 – 10.5 12.6 – 10.0 13.0 – 10.5 V V CMRR Common Mode Rejection Ratio VCM = –10V to 12.6V ● 78 99 76 94 dB PSRR Power Supply Rejection Ratio VS = ±4.5V to ± 20V ● 81 96 79 93 dB AVOL Large-Signal Voltage Gain VO = ±12V, RL = 10k VO = ±10V, RL = 1k ● ● 850 400 3300 2200 750 300 3000 2000 V/mV V/mV VOUT Output Voltage Swing RL = 10k RL = 1k ● ● ±12.8 ±11.8 ±13.1 ±12.1 ±12.8 ±11.8 ±13.1 ±12.1 V V SR Slew Rate RL ≥ 2k ● 2.1 3.2 2.1 3.2 GBW Gain-Bandwidth Product fO = 100kHz ● 2 3.1 2 3.1 IS Supply Current VS = ±5V ● ● SYMBOL PARAMETER VOS Input Offset Voltage ∆VOS ∆Temp Average Input Offset Voltage Drift IOS CONDITIONS (Note 2) Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Typical parameters are defined as the 60% yield of parameter distributions of individual amplifiers. Note 3: IB and IOS readings are extrapolated to a warmed-up temperature from 25°C measurements and 32°C characterization data. Note 4: Current noise is calculated from the formula: in = (2qIB)1/2 where q = 1.6 • 10 –19 coulomb. The noise of source resistors up to 200M swamps the contribution of current noise. Note 5: Input voltage range functionality is assured by testing offset voltage at the input voltage range limits to a maximum of 2.3mV (A grade) to 2.8mV (C grade). 4 4.2 4.2 5.40 5.35 4.2 4.2 UNITS V/µs MHz 5.40 5.35 mA mA Note 6: This parameter is not 100% tested. Note 7: Slew rate is measured in AV = –1; input signal is ±7.5V, output measured at ±2.5V. Note 8: The LT1793AC and LT1793C are guaranteed to meet specified performance from 0°C to 70°C and are designed, characterized and expected to meet these extended temperature limits, but are not tested at – 40°C and 85°C. The LT1793I is guaranteed to meet the extended temperature limits. The LT1793AC and LT1793AI grade are 100% temperature tested for the specified temperature range. Note 9: The LT1793 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 10°C to 50°C higher than the ambient temperature. LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS 1kHz Input Noise Voltage Distribution 0.1Hz to 10Hz Voltage Noise Voltage Noise vs Frequency 100 50 PERCENT OF UNITS (%) VOLTAGE NOISE (1µV/DIV) 40 RMS VOLTAGE NOISE DENSITY (nV/√Hz) TA = 25°C VS = ±15V 510 OP AMPS TESTED 30 20 10 2 4 6 TIME (SEC) 8 1793 G01 V+ VS = ±15V 1 8 7 6 5 4 + V = 5V TO 20V –1.5 –2.0 4.0 3.5 V – = – 5V TO – 20V 3.0 V – +2.0 –60 100 125 60 100 20 TEMPERATURE (°C) 80 60 40 20 1k 140 10k 100k 1M FREQUENCY (Hz) 10M 1793 G06 Gain and Phase Shift vs Frequency Voltage Gain vs Frequency 180 TA = 25°C 160 100 140 TA = 25°C VS = ±15V CL = 10pF 40 120 100 80 60 40 20 30 80 100 120 PHASE 20 140 10 160 GAIN 0 PHASE SHIFT (DEG) VOLTAGE GAIN (dB) +PSRR 50 TA = 25°C VS = ±15V CL = 10pF VOLTAGE GAIN (dB) 120 20 100 1793 G05 Power Supply Rejection Ratio vs Frequency 40 TA = 25°C VS = ± 15V 0 –20 1793 G04 –PSRR 10k Common Mode Rejection Ratio vs Frequency 2.5 60 100 1k FREQUENCY (Hz) 120 –1.0 3 80 10 1793 G03 0 –0.5 9 COMMON MODE LIMIT (V) REFERRED TO POWER SUPPLY VOLTAGE NOISE (AT 1kHz) (nV/√Hz) 1 Common Mode Limit vs Temperature 2 –75 –50 –25 0 25 50 75 TEMPERATURE (°C) POWER SUPPLY REJECTION RATIO (dB) 1/f CORNER 30Hz 1793 G02 Voltage Noise vs Chip Temperature 10 10 0 4.2 4.6 5.0 5.4 5.8 6.2 6.6 7.0 7.4 7.8 8.2 INPUT VOLTAGE NOISE (nV/√Hz) 10 COMMON MODE REJECTION RATIO (dB) 0 TA = 25°C VS = ±15V 180 0 0 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M 1793 G07 – 20 0.01 –10 1 10k 100 FREQUENCY (Hz) 1M 100M 1793 G08 0.1 1 10 FREQUENCY (MHz) 200 100 1793 G09 5 LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Swing vs Load Current Large-Signal Transient Response Small-Signal Transient Response V + –0.8 OUTPUT VOLTAGE SWING (V) 5V/DIV 20mV/DIV AV = 1 CL = 10pF VS = ±15V, ±5V 1793 G10 1µs/DIV AV = 1 CL = 10pF RL = 2k VS = ±15V 1793 G11 5µs/DIV 125°C 25°C –1.0 –1.2 –55°C –1.4 –1.6 VS = ±5V TO ±20V 2.0 1.8 1.6 125°C 1.4 1.2 25°C –55°C V – +1.0 –10 –8 –6 –4 –2 0 2 4 6 8 10 ISINK ISOURCE OUTPUT CURRENT (mA) 1793 G12 30 20 AV = 1 10 VS = ±15V TA = 25°C 75 TOTAL HARMONIC DISTORTION + NOISE (%) OVERSHOOT (%) 40 90 VS = ±15V TA = 25°C RL ≥ 10k VO = 100mVP-P AV = 10 RF = 10k CF = 20pF CHANGE IN OFFSET VOLTAGE (µV) 50 THD and Noise Frequency for Noninverting Gain Warm-Up Drift Capacitive Load Handling SO-8 PACKAGE 60 45 N8 PACKAGE 30 15 AV = 10 0 1 100 1000 10 CAPACITIVE LOAD (pF) 10000 5 2 3 4 1 TIME AFTER POWER ON (MINUTES) 0.1 AV = – 100 0.01 AV = – 10 AV = – 1 0.001 NOISE FLOOR 0.0001 20 100 1k FREQUENCY (Hz) 10k 20k 1793 G16 6 AV = 100 0.01 AV = 10 AV = 1 0.001 NOISE FLOOR 6 20 100 1k FREQUENCY (Hz) THD and Noise vs Output Amplitude for Noninverting Gain 1 0.1 ZL = 2k 15pF, fO = 1kHz AV = –1, –10, –100 MEASUREMENT BANDWIDTH = 10Hz TO 22kHz AV = –100 0.01 AV = –10 0.001 AV = –1 0.0001 0.3 1 10 OUTPUT SWING (VP-P) 10k 20k 1793 G15 THD and Noise vs Output Amplitude for Inverting Gain TOTAL HARMONIC DISTORTION + NOISE (%) TOTAL HARMONIC DISTORTION + NOISE (%) THD and Noise vs Frequency for Inverting Gain ZL = 2k 15pF VO = 20VP-P AV = – 1, – 10, – 100 MEASUREMENT BANDWIDTH = 10Hz TO 80kHz 0.1 1793 G14 1793 G13 1 ZL = 2k 15pF VO = 20VP-P AV = 1, 10, 100 MEASUREMENT BANDWIDTH = 10Hz TO 80kHz 0.0001 0 TOTAL HARMONIC DISTORTION + NOISE (%) 0 0.1 1 30 1793 G17 1 0.1 ZL = 2k 15pF, fO = 1kHz AV = 1, 10, 100 MEASUREMENT BANDWIDTH = 10Hz TO 22kHz AV = 100 0.01 AV = 10 0.001 AV = 1 0.0001 0.3 1 10 OUTPUT SWING (VP-P) 30 1793 G18 LT1793 U W TYPICAL PERFOR A CE CHARACTERISTICS Short-Circuit Output Current vs Temperature 30 SINK SOURCE 25 20 15 10 – 75 – 50 – 25 0 25 50 75 TEMPERATURE (°C) INPUT BIAS AND OFFSET CURRENTS (A) 35 OUTPUT CURRENT (mA) 30n 5 VS = ±15V SUPPLY CURRENT PER AMPLIFIER (mA) 40 VS = ±15V 4 VS = ± 5V 3 – 75 – 50 – 25 0 25 50 75 TEMPERATURE (°C) 100 125 100 125 1793 G19 W U UO INPUT BIAS CURRENT (pA) 1n BIAS CURRENT 300p 100p 30p OFFSET CURRENT 10p 3p 1p 0.3p 0 25 75 100 50 TEMPERATURE (°C) 125 1793 G21 S I FOR ATIO With improved noise performance, the LT1793 in the PDIP directly replaces such JFET op amps as the OPA111 and the AD645. The combination of low current and voltage noise of the LT1793 allows it to surpass most dual and single JFET op amps. The LT1793 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 LT1793 when transducer impedance increases. CURRENT NOISE = √2qIB The extremely high input impedance (1013Ω) assures that the input bias current is almost constant over the entire common mode range. Figure 1 shows how the LT1793 stands up to the competition. Unlike the competition, as the input voltage is swept across the entire common mode range the input bias current of the LT1793 hardly changes. As a result the current noise does not degrade. This makes the LT1793 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 60 15V 15V 40 OP215 20 LT1793 2 – 3 + 7 2 – 3 + 7 6 6 0 –20 –40 3n 1793 G20 LT1793 vs the Competition 80 VS = ±15V VCM = –10 TO 13V 10n U APPLICATI 100 Input Bias and Offset Currents vs Chip Temperature Supply Current vs Temperature 4 AD822 5 ∆VOS = ±13mV 1 –60 4 5 10k 50k ∆VOS = ±1.3mV 1 10k –80 –100 –15 – 15V –10 0 5 10 –5 COMMON MODE RANGE (V) 50k 15 – 15V 1793 F01 Figure 1. Comparison of LT1793, OP215, and AD822 Input Bias Current vs Common Mode Range (a) 1793 F02 (b) Figure 2 7 LT1793 W U U UO S I FOR ATIO APPLICATI with temperature will occur when the device is nulled with a potentiometer ranging from 10k to 200k. 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 LT1793 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 10k LT1007* INPUT NOISE VOLTAGE (nV/√ H z) CS – 1k LT1793* RS + VO RS 100 CS LT1007† LT1793 10 LT1793† 1 100 Optimization Techniques for Charge Amplifiers LT1007 RESISTOR NOISE ONLY 1k voltage noise, the thermal noise of the transducer, and the op amp’s input bias current noise times the transducer impedance. Figure 3 shows total input voltage noise versus source resistance. In a low source resistance (< 5k) application the op amp voltage noise will dominate the total noise. This means the LT1793 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 5k to 50k, the LT1793 will match the best bipolar op amps for noise performance, since the thermal noise of the transducer (4kTR) begins to dominate the total noise. A further increase in source resistance, above 50k, is where the op amp’s current noise component (2qIBR2) will eventually dominate the total noise. At these high source resistances, the LT1793 will out perform the lowest noise bipolar op amps due to the inherently low current noise of FET input op amps. Clearly, the LT1793 will extend the range of high impedance transducers that can be used for high signal-to-noise ratios. This makes the LT1793 the best choice for high impedance, capacitive transducers. 10k 100k 1M 10M 100M SOURCE RESISTANCE (Ω) 1G 1793 F03 SOURCE RESISTANCE = 2RS = R * PLUS RESISTOR † PLUS RESISTOR 1000pF CAPACITOR Vn = AV √Vn2(OP AMP) + 4kTR + 2qIBR2 Figure 3. Comparison of LT1793 and LT1007 Total Output 1kHz Voltage Noise vs Source Resistance The high input impedance JFET front end makes the LT1793 suitable in applications where very high charge sensitivity is required. Figure 4 illustrates the LT1793 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 LT1793. The charge across the transducer capacitance CS is transferred to the feedback capacitor CF RF R2 CB CF RB – CS RS + TRANSDUCER CB RB OUTPUT CB = CF CS RB = RF RS dQ dV Q = CV; = I = C dt dt – R1 OUTPUT + CS RS CB ≅ CS RB = RS RS > R1 OR R2 TRANSDUCER Figure 4. Inverting and Noninverting Gain Configurations 8 1793 F04 LT1793 W U U UO APPLICATI S I FOR ATIO resulting in a change in voltage dV, which is equal to dQ/CF. The gain therefore is CF/CS. For unity-gain, the CF should equal the transducer capacitance plus the input capacitance of the LT1793 and RF should equal RS. In the noninverting mode example, the transducer current is converted to a change in voltage by the transducer capacitance, CS. This voltage is then buffered by the LT1793 with a gain of 1 + R1/R2. A DC path is provided by RS, which is either the transducer impedance or an external resistor. Since RS is usually several orders of magnitude greater than the parallel combination of R1 and R2, R B is added to balance the DC offset caused by the noninverting input bias current and RS. The input bias currents, although small at room temperature, can create significant errors at higher temperature, especially with transducer resistances of up to 1000M or more. The optimum value Input: ±5.2V Sine Wave for RB is determined by equating the thermal noise (4kTRS) to the current noise (2qIB) times RS2. Solving for RS results in RB = RS = 2VT/IB (VT = 26mV at 25°C). A parallel capacitor CB, is used to cancel the phase shift caused by the op amp input capacitance and RB. Reduced Power Supply Operation To take full advantage of a wide input common mode range, the LT1793 was designed to eliminate phase reversal. Referring to the photographs in Figure 5, the LT1793 is shown operating in the follower mode (AV = 1) at ±5V supplies with the input swinging ±5.2V. The output of the LT1793 clips cleanly and recovers with no phase reversal. This has the benefit of preventing lockup in servo systems and minimizing distortion components. LT1793 Output LT1793 F05a LT1793 F05b Figure 5. Voltage Follower with Input Exceeding the Common Mode Range (VS = ±5V) 9 LT1793 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.100 ± 0.010 (2.540 ± 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 10 0.130 ± 0.005 (3.302 ± 0.127) 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1197 LT1793 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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 0996 11 LT1793 U TYPICAL APPLICATIONS N 10Hz Fourth Order Chebyshev Lowpass Filter (0.01dB Ripple) R2 237k R1 237k VIN C2 100nF R3 249k R5 154k 15V 2 3 – + C1 33nF 7 6 LT1793 R4 154k R6 249k C4 330nF 4 2 – 3 + C3 10nF LT1793 6 VOUT 1793 TA04 –15V TYPICAL OFFSET ≈ 0.8mV 1% TOLERANCES FOR VIN = 10VP-P, VOUT = –121dB AT f > 330Hz = – 6dB AT f = 16.3Hz LOWER RESISTOR VALUES WILL RESULT IN LOWER THERMAL NOISE AND LARGER CAPACITORS Accelerometer Amplifier with DC Servo C1 1250pF R1 100M R2 18k R3 2k C2 2µF – 5V TO 15V ACCELEROMETER B & K MODEL 4381 OR EQUIVALENT (800) 442-1030 2 – 3 3 R5 20M C3 2µF 7 LT1793 R4 20M 1/2 LT1464 + 1 2 6 OUTPUT + 1793 TA03 4 –5V TO –15V R4C2 = R5C3 > R1 (1 + R2/R3) C1 OUTPUT = 0.8mV/pC* = 8.0mV/g** DC OUTPUT ≤ 1.9mV OUTPUT NOISE = 8nV/√ Hz AT 1kHz *PICOCOULOMBS **g = EARTH’S GRAVITATIONAL CONSTANT RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1113 Low Noise, Dual JFET Op Amp Dual Version of LT1792, VNOISE = 4.5nV/√Hz LT1169 Low Noise, Dual JFET Op Amp Dual Version of LT1793, VNOISE = 6nV/√Hz, IB = 10pA LT1467 Micropower Dual JFET Op Amp 1MHz, 2pA Max IB, 200µA Max IS LT1792 Low Noise, Single JFET Op Amp Lower VNOISE Version of LT1793, VNOISE = 4.2nV/√Hz 12 Linear Technology Corporation 1793f LT/TP 0599 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1999