36 V, 19 MHz, Low Noise, Low Bias Current, JFET Operational Amplifier ADA4627-1 PIN CONFIGURATIONS Low offset voltage: 200 μV maximum Offset drift: 1 μV/°C typical Very low input bias current: 5 pA maximum Extended temperature range: −40ºC to +125ºC ±5 V to ±15 V dual-supply Guaranteed GBW: 16 MHz Voltage noise: 6.1 nV/√Hz at 1 kHz High slew rate: 60 V/μs High gain: 120 dB typical High CMRR: 116 dB typical High PSRR: 112 dB typical Low supply current: 7.5 mA maximum NULL 1 –IN 2 ADA4627-1 +IN 3 TOP VIEW (Not to Scale) V– 4 8 NC 7 V+ 6 OUT 5 NULL NC = NO CONNECT 07559-001 FEATURES Figure 1. 8-Lead SOIC_N (R-8) +IN 3 V– 4 APPLICATIONS PIN 1 INDICATOR 8 NC ADA4627-1 7 V+ TOP VIEW (Not toScale) 5 NC 6 OUT NOTES 1. NC = NO CONNECT. 2. CONNECT EXPOSED PAD TO GROUND. High impedance sensors Photo diode amplifier Precision instrumentation Phase-locked loop filters High end, professional audio DAC output amplifier ATE Medical 07559-002 NC 1 –IN 2 Figure 2. 8-Lead LFCSP_VD (CP-8-2) GENERAL DESCRIPTION The ADA4627-1 is a wide bandwidth precision amplifier featuring low noise, very low offset, drift, and bias current. Operation is specified from ±5 V to ±15 V dual supply. The ADA4627-1 provides benefits previously found in few amplifiers. This amplifier combines the best specifications of precision dc and high speed ac op amps. With a typical offset voltage of only 70 μV, drift of less than 1 μV/°C, and noise of only 0.86 μV p-p (0.1 Hz to 10 Hz), the ADA4627-1 is suited for applications in which error sources cannot be tolerated. ature range of −40°C to +125°C. It is available in tiny 8-lead LFCSP and 8-lead SOIC packages. The ADA4627-1 is a member of a growing series of high speed, precision op amps offered by Analog Devices, Inc (see Table 1). Table 1. High Speed Precision Op Amps Supply Single Dual 5 V Low Cost AD8615 AD8616 Quad AD8618 5V AD8651 AD8652 26 V Low Power AD8610 AD8620 30 V Low Cost AD8510 AD8512 30 V ADA4627-1 AD8513 The ADA4627-1 is specified for both the industrial temperature range of −25°C to +85°C and the extended industrial temper- Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2009 Analog Devices, Inc. All rights reserved. ADA4627-1 TABLE OF CONTENTS Features .............................................................................................. 1 Input Voltage Range ................................................................... 12 Applications ....................................................................................... 1 Input Offset Voltage Adjust Range........................................... 12 Pin Configurations ........................................................................... 1 Input Bias Current ...................................................................... 12 General Description ......................................................................... 1 Noise Considerations ................................................................. 12 Revision History ............................................................................... 2 THD + N Measurements ........................................................... 12 Specifications..................................................................................... 3 Electrical Characteristics—30 V Operation ............................. 3 Printed Circuit Board Layout, Bias Current, and Bypassing ..................................................................................... 13 Absolute Maximum Ratings............................................................ 5 Output Phase Reversal ............................................................... 13 Thermal Resistance ...................................................................... 5 Driving Capacitive Loads .......................................................... 13 ESD Caution .................................................................................. 5 Outline Dimensions ....................................................................... 14 Typical Performance Characteristics ............................................. 6 Ordering Guide .......................................................................... 15 Theory of Operation ...................................................................... 12 REVISION HISTORY 9/09—Rev. 0 to Rev. A Changes to General Description Section ...................................... 1 Changes to Table 2 ............................................................................ 3 Updated Outline Dimensions ....................................................... 14 Changes to Ordering Guide .......................................................... 15 7/09—Revision 0: Initial Version Rev. A | Page 2 of 16 ADA4627-1 SPECIFICATIONS ELECTRICAL CHARACTERISTICS—30 V OPERATION VSY = ±15 V, VCM = 0 V, TA = 25°C, unless otherwise noted. Table 2. B Grade Parameter INPUT CHARACTERISTICS Offset Voltage 1 Symbol Conditions Min VOS Offset Voltage Drift, Average Power Supply Rejection Ratio ∆VOS/∆T PSRR Input Bias Current 2 IB −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C VSY = ±4.5 V to ±18 V −40°C ≤ TA ≤ +125°C 106 101 Max 70 200 350 400 2 1 112 1 −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +125°C Input Offset Current IOS 0.5 −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +125°C NOISE PERFORMANCE Voltage Noise Density Voltage Noise Current Noise Density Current Noise Input Resistance Input Capacitance, Differential Mode Input Capacitance, Common Mode Input Voltage Range en en p-p in In p-p RIN CINDM 16.5 7.9 6.1 4.8 0.69 1.6 30 10 8 CINCM Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain AVO DYNAMIC PERFORMANCE Slew Rate f = 10 Hz f = 100 Hz f = 1 kHz f = 10 kHz 0.1 Hz to 10 Hz f = 100 Hz 0.1 Hz to 10 Hz SR SR Settling Time to 0.01% tS Settling Time to 0.1% tS Gain Bandwidth Product Phase Margin Total Harmonic Distortion + Noise GBP ΦM THD + N A Grade Typ Min 103 99 10 V step, RL = 1 kΩ, CL = 100 pF, AV = +1 10 V step, RL = 1 kΩ, CL =100 pF, Rs = Rf = 1 kΩ AV = −1 VIN = 10 V step, CL = 35 pF, RL = 1 kΩ, AV = −1 VIN = 10 V step, CL = 35 pF, RL = 1 kΩ, AV = −1 RL = 1 kΩ, CL = 20 pF, AV = 1 RL = 1 kΩ, CL = 20 pF, AV = 1 f = 1 kHz, AV = 1 −11 −10.5 106 98 112 110 102 120 Unit 120 300 410 660 3 μV 1 108 1 40 20 8 6 1.6 16.5 7.9 6.1 4.8 0.69 2.5 48 10 8 0.5 −11 −10.5 100 97 106 104 100 110 μV μV/°C dB dB pA nA nA pA nA nA nV/√Hz nV/√Hz nV/√Hz nV/√Hz μV p-p fA/√Hz fA p-p TΩ pF pF V V dB 120 dB dB dB V/μs 56/78 3 40 56/783 40 82/843 40 82/843 Rev. A | Page 3 of 16 40 20 8 6 1.6 +11 +10.5 40 16 4 5 0.5 2 5 0.5 2 7 +11 +10.5 116 Max 5 0.5 2 5 0.5 2 7 −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C, VCM = −11 V to +11 V VCM = −10.5 V to +10.5 V RL = 1 kΩ, VO = −10 V to +10 V −40 ≤ TA ≤ +85°C −40 ≤ TA ≤ +125°C Typ 550 550 ns 450 450 ns 19 72 0.000045 MHz Degrees % 19 72 0.000045 164 ADA4627-1 B Grade Parameter POWER SUPPLY Supply Current per Amplifier Symbol Conditions ISY IO = 0 mA −40°C ≤ TA ≤ +125°C OUTPUT CHARACTERISTICS Output Voltage High VOH Output Voltage Low VOL Output Current Short-Circuit Current Closed-Loop Output Impedance Iout ISC ZOUT RL = 1 kΩ to VCM −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +125°C RL = 1 kΩ to VCM −40°C ≤ TA ≤ +85°C −40°C ≤ TA ≤ +125°C VO = ±10 V TA = 25°C f = 1 MHz, AV = −100 Min 12.0 11.8 11.7 Max ±7.0 ±7.5 ±7.8 12.3 −12.7 ±45 +70/−55 41 1 VOS is measured fully warmed-up. Tested/extrapolated from 125°C 3 Rising/falling. 4 Not tested. Guaranteed by simulation and characterization. 2 Rev. A | Page 4 of 16 A Grade Typ −12.3 −12.1 −12.0 Min 12.0 11.8 11.7 −12.7 Typ Max Unit ±7.0 ±7.5 ±7.8 mA mA 12.3 −12.3 −12.1 −12.0 ±45 +70/−55 41 V V V V V V mA mA Ω ADA4627-1 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 3. Parameter Supply Voltage Input Voltage Range 1 Input Current1 Differential Input Voltage2 Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) ESD Human Body Model Rating 36 V (V−) − 0.3 V to (V+) + 0.3 V ±10 mA ±VSY Indefinite −65°C to +150°C −40°C to +125°C −65°C to +150°C 300°C 2.5 kV θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. This was measured using a standard two-layer board. For the LFCSP package, the exposed pad should be soldered to a copper plane. Table 4. Thermal Resistance Package Type 8-Lead SOIC_N (R-8) 8-Lead LFCSP (CP-8-2) ESD CAUTION 1 Input pin has clamp diodes to the power supply pins. Input current should be limited to 10 mA or less whenever input signals exceed the power supply rail by 0.3 V. 2 Differential input voltage is limited to ±30 V or the supply voltage, whichever is less. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rev. A | Page 5 of 16 θJA 155 77 θJC 45 14 Unit °C/W °C/W ADA4627-1 TYPICAL PERFORMANCE CHARACTERISTICS 120 270 100 225 80 180 60 135 78° 40 45 20 0 0 ADA4627-1 TA = 25°C VSY = ±15V ADA4627-1 TA = 25°C VSY = ±15V –20 1 0.01 0.1 1 FREQUENCY (kHz) 10 –40 1k 10k Figure 3. Voltage Noise Density –45 100k 1M FREQUENCY (Hz) –90 100M 10M 100 RL = 1kΩ 120 10 AV = –10 ADA4627-1 TA = 25°C VSY = ±15V 0 25 50 TEMPERATURE (°C) 75 100 125 0.01 100 Figure 4. Open-Loop Gain vs. Temperature 100 100 80 50 VOS (µV) 150 60 40 10k 100k 1M FREQUENCY (Hz) 10M 100M 0 –50 ADA4627-1 TA = 25°C VSY = ±15V 1k ADA4627-1 TA = 25°C VSY = ±15V –100 07559-010 0 100 1k Figure 7. Closed-Loop ZOUT vs. Frequency 120 20 AV = –1 07559-007 –25 AV = –100 0.1 ADA4627-1 TA = 25°C VSY = ±15V VO = ±11V 60 –50 1 10k 100k FREQUENCY (Hz) 1M –150 –15 10M Figure 5. CMRR vs. Frequency –10 5 07559-069 80 ZOUT (Ω) RL = 600Ω 100 07559-004 OPEN-LOOP GAIN (dB) 19.1MHz Figure 6. Open-Loop Gain and Phase vs. Frequency 140 CMRR (dB) 90 07559-006 GAIN (dB) 10 07559-003 VOLTAGE NOISE DENSITY (nV√Hz) 100 PHASE (Degrees) TA = 25°C, unless otherwise noted. 0 VCM (V) 5 Figure 8. VOS vs. Common-Mode Voltage Rev. A | Page 6 of 16 10 15 ADA4627-1 TA = 25°C, unless otherwise noted. 120 100 60 PSRR– PSRR+ 40 ADA4627-1 TA = 25°C VSY = ±15V 20 0 100 1k 10k 100k 1M 10M FREQUENCY (Hz) 100 90 80 70 60 –50 07559-009 PSRR (dB) 80 110 –25 0 25 50 75 100 125 TEMPERATURE (°C) Figure 9. PSRR vs. Frequency Figure 12. CMRR vs. Temperature 8 20 –40ºC ADA4627-1 TA = 25°C VSY = ±15V 7 +25ºC 6 +85ºC +125ºC 10 5 VOL – VSS (V) SUPPLY CURRENT (mA) ADA4627-1 VSY = ±15V VCM = ±11.5V 07559-012 COMMON-MODE REJECTION RATIO (dB) 120 4 3 ADA4627-1 TA = 25°C 2 0 4 8 12 16 20 24 SUPPLY VOLTAGE (V) 28 32 36 1 0.001 07559-011 0 07559-058 1 0.01 0.1 1 ILOAD (mA) 10 100 Figure 13. VOUT Sinking vs. ILOAD Current Figure 10. Supply Current vs. Supply Voltage and Temperature 20 120 ADA4627-1 TA = 25°C VSY = ±15V ADA4627-1 RL = 1kΩ ±4.5V < VSY < ±15V 100 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 1 0.001 120 Figure 11. PSRR vs. Temperature 07559-057 VDD – VOH (V) 110 07559-068 PSRR (dB) 10 0.01 0.1 1 ILOAD (mA) 10 Figure 14. VOUT Sourcing vs. ILOAD Current Rev. A | Page 7 of 16 100 ADA4627-1 TA = 25°C, unless otherwise noted. 0.01 8 ADA4627-1 TA = 25°C VSY = ±15V VIN = 810mV RL = 600Ω 80kHz FILTER 6 0.001 THD + N (%) 5 4 3 0.0001 2 0 0 4 8 12 16 20 24 28 32 SUPPLY VOLTAGE (V) 36 07559-071 ADA4627-1 TA = 25°C SOIC PACKAGE 1 0.00001 0.01 07559-015 SUPPLY CURRENT (mA) 7 0.1 1 FREQUENCY (kHz) 10 Figure 18. THD + N vs. Frequency Figure 15. Supply Current vs. Supply Voltage 10,000 0.1 ADA4627-1 VSY = ±15 1,000 0.01 MEASURED IB (pA) THD + N (%) 100 0.001 10 0.00001 0.001 EXTRAPOLATED 1 y = 0.2895 0.0647x R2 = 0.9991 07559-072 0.0001 0.01 0.1 AMPLITUDE (V rms) 0.1 1 10 30 07559-078 ADA4627-1 TA = 25°C VSY = ±15V VIN = 1kHz RL = 600Ω 80kHz FILTER 50 70 90 TEMPERATURE (°C) 110 130 Figure 19. Input Bias Current vs. Temperature Figure 16. THD + N vs. VIN 100 60 ADA4627-1 TA = 25°C VSY = ±15 50 IB+ 75 +85°C 50 40 IB– 25 IB (pA) 20 AV = +10 10 IB+ +25ºC 0 IB– –25 0 –50 AV = +1 –20 10 100 1k 10k 100k FREQUENCY (kHz) 1M 10M ADA4627-1 VSY = ±15V –75 –100 –15 100M Figure 17. Closed-Loop Gain vs. Frequency –10 07559-073 –10 07559-070 GAIN (dB) AV = +100 30 –5 0 VCM (V) 5 10 Figure 20. Input Bias Current vs. VCM and Temperature Rev. A | Page 8 of 16 15 ADA4627-1 TA = 25°C, unless otherwise noted. 1200 1100 OUTPUT VOLTAGE (5V/DIV) IB+ 900 IB (pA) 800 IB– 700 600 500 400 300 100 0 –15 –10 ADA4627-1 TA = 25°C AV = –1 VIN = 20V p-p RF = RIN = 2kΩ CF = 10pF RL = 1kΩ CL = 1nF 07559-074 ADA4627-1 TA = 125°C VSY = ±15V 200 1 –5 0 VCM (V) 5 10 07559-061 1000 TIME (1µs/DIV) 15 Figure 24. Large Signal Transient Response Figure 21. Input Bias Current vs. VCM at 125°C 80 ADA4627-1 TA = 25°C VSY = ±15V OUTPUT VOLTAGE (5V/DIV) 60 40 VOS (µV) 20 0 –20 –80 07559-075 –60 1 07559-062 –40 ADA4627-1 TA = 25°C AV = +1 VIN = 20V p-p RF = 0Ω 0 60 120 180 TIME (Seconds) 240 TIME (200ns/DIV) 300 Figure 25 Large Signal Transient Response Figure 22. Input Offset Voltage vs. Time 60 OUTPUT VOLTAGE (5V/DIV) OS– 40 20 TA = 25°C VSY = ±15V AV = +1 VIN = 100mV p-p 10 0 1 10 100 1000 LOAD CAPACITANCE (pF) 1 07559-059 OS+ 30 07559-023 OVERSHOOT (%) 50 ADA4627-1 TA = 25°C AV = –1 VIN = 20V p-p RF = RIN = 2kΩ CH1 5.00V 10,000 TIME (200ns/DIV) Figure 26. Large Signal Transient Response Figure 23. Small Signal Overshoot vs. Load Capacitance Rev. A | Page 9 of 16 ADA4627-1 ADA4627-1 TA = 25°C AV = –1 VIN = 200mV p-p RF = RIN = 2kΩ CF = 5pF TIME (1µs/DIV) TIME (200ns/DIV) Figure 30. Small Signal Transient Response 1 1 ADA4627-1 TA = 25°C AV = +1 VIN = 200mV p-p RF = 0Ω RL = 1kΩ CL = 1nF TIME (200ns/DIV) TIME (200ns/DIV) Figure 31. Small Signal Transient Response OUTPUT VOLTAGE (50mV/DIV) Figure 28. Large Signal Transient Response 1 ADA4627-1 TA = 25°C AV = +1 VIN = 200mV p-p RF = 0Ω 07559-064 OUTPUT VOLTAGE (50mV/DIV) 07559-065 OUTPUT VOLTAGE (50mV/DIV) ADA4627-1 TA = 25°C AV = –1 VIN = 20V p-p RF = RIN = 2kΩ CF = 10pF RL = 1kΩ CL = 100pF 07559-060 OUTPUT VOLTAGE (5V/DIV) Figure 27. Large Signal Transient Response 1 ADA4627-1 TA = 25°C AV = –1 VIN = 200mV p-p RF = RIN = 2kΩ CF = 5pF RL = 1kΩ CL = 100pF TIME (200ns/DIV) TIME (200ns/DIV) Figure 32. Small Signal Transient Response Figure 29. Small Signal Transient Response Rev. A | Page 10 of 16 07559-067 ADA4627-1 TA = 25°C AV = +1 VIN = 20V p-p RF = 0Ω RL = 1kΩ CL = 1nF 1 07559-066 OUTPUT VOLTAGE (50mV/DIV) 1 07559-063 OUTPUT VOLTAGE (5V/DIV) TA = 25°C, unless otherwise noted. ADA4627-1 TA = 25°C, unless otherwise noted. ADA4627-1 TA = 25°C VSY = ±15V 10 5 0 –5 VOUT –10 VOUT 2 VIN 07559-077 –15 VIN 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 TIME (ms) TIME (200ns/DIV) 07559-033 –20 Figure 35. Positive Settling Time to 0.01% VIN 2 VOUT 07559-076 INPUT VOLTAGE (5V/DIV) 1 OUTPUT VOLTAGE (1mV/DIV) ADA4627-1 TA = 25°C VSY = ±15 OUTPUT VOLTAGE (200mV/DIV) Figure 33. No Phase Reversal TIME (200ns/DIV) 1 ADA4627-1 TA = 25°C VSY = ±15V DUT GAIN = 100 4TH ORDER BAND PASS FIXTURE GAIN = 10k TOTAL GAIN = 1M TIME (1s/DIV) Figure 34. Negative Settling Time to 0.01% Figure 36. 0.1 Hz to 10 Hz Noise Rev. A | Page 11 of 16 07559-040 AMPLITUDE (V) ADA4627-1 TA = 25°C VSY = ±15 1 INPUT VOLTAGE (5V/DIV) 15 OUTPUT VOLTAGE (1mV/DIV) 20 ADA4627-1 THEORY OF OPERATION chain. Signal chain offset can be addressed with an autozero amplifier used to form a composite amplifier, or if the ADA4627-1 is at an inverting amplifier stage, it can be modified easily to create a summing amplifier where a potentiometer can be added (see Figure 38). The LFCSP package does not have offset adjust pins. RF INPUT VOLTAGE RANGE RIN The ADA4627-1 is not a rail-to-rail input amplifier, thus, care is required to ensure that both inputs do not exceed the input voltage range. Under normal negative feedback operating conditions, the amplifier corrects its output to ensure that the two inputs are at the same voltage. However, if either input exceeds the input voltage range, the loop opens and large currents begin to flow through the ESD protection diodes in the amplifier. These diodes are connected between the inputs and each supply rail to protect the input transistors against an electrostatic discharge event, and they are normally reverse-biased. However, if the input voltage exceeds the supply voltage, these ESD diodes can become forward-biased. Without current limiting, excessive amounts of current may flow through these diodes, causing permanent damage to the device. If inputs are subject to overvoltage, insert appropriate series resistors to limit the diode current to less than 5 mA. INPUT OFFSET VOLTAGE ADJUST RANGE The ADA4627-1 SOIC package has offset adjust pins for compatibility with some existing designs. The recommended offset nulling circuit is shown in Figure 37. +VS 2 ADA4627-1 + VIN 3 +VS – 499kΩ 6 499kΩ 200Ω 0.1µF + VOUT – 100kΩ –VS 07559-052 The ADA4627-1 is a high speed, unity gain stable amplifier with excellent dc characteristics. The typical offset voltage of 70 μV allows the amplifier to be easily configured for high gains without the risk of excessive output voltage errors. The small temperature drift of 2 μV/°C ensures a minimum offset voltage error over the entire temperature range of −40°C to +125°C, making the amplifier ideal for a variety of sensitive measurement applications in harsh operating environments. Figure 38. Alternate Offset Null Circuit for Inverting Stage INPUT BIAS CURRENT Because the ADA4627-1 has a JFET input stage, the input bias current, due to the reverse-biased junction, has a leakage current that approximately doubles every 10°C. The power dissipation of the part, combined with the thermal resistance of the package, results in the junction temperature increasing 20 to 30 degrees Centigrade above ambient. This parameter is tested with high speed ATE equipment, which does not result in the die temperature reaching equilibrium. This is correlated with bench measurements to match the guaranteed maximum at room temperature in Table 2. The input current can be reduced by keeping the temperature as low as possible and using a light load on the output. NOISE CONSIDERATIONS The JFET input stage offers very low input voltage noise and input current noise. The thermal noise of a 1 kΩ resistor at room temperature is 4 nV/√Hz, thus low values of resistance should be used for dc-coupled inverting and noninverting amplifier configurations. In the case of transimpedance amplifiers (TIAs), current noise is more important. 100kΩ 7 1 2 5 ADA4627-1 6 3 –VS 07559-051 4 Figure 37. Standard Offset Null Circuit With a 100 kΩ potentiometer, the adjustment range is more than ±11 mV. However, the VOS temperature drift increases by several μV/°C for every millivolt of offset adjust. The ADA4627-1 has matching thin film resistors that are laser trimmed at two temperatures to minimize both offset voltage and offset voltage drift. The offset voltage at room temperature is less than 0.5 mV, and the offset voltage drift is only a few μV/ºC or less, therefore, it is not recommended to use the offset adjust pins, especially for offset adjust of a complete signal The ADA4627-1 is an excellent choice for both of these applications. Analog Devices offers a wide variety of low voltage noise and low current noise op amps in a variety of processes optimized for different supply voltage ranges. Refer to Application Note AN-940 for a complete discussion of noise, calculations, and selection tables for more than three dozen low noise, op amp families. THD + N MEASUREMENTS Total harmonic distortion plus noise (THD + N) is usually measured with an audio analyzer from Audio Precision, Inc. The analyzer consists of a low distortion oscillator that is swept from the starting frequency to the ending frequency. The Rev. A | Page 12 of 16 ADA4627-1 The analyzer has a tunable notch filter in lock step with the swept oscillator. This removes the fundamental frequency, but allows all of the harmonics and wideband noise to be measured with an integrating voltmeter. However, there is a switchable low-pass filter in series with the notch filter. If the sine wave is at 100 Hz, then the tenth harmonic is still at 1 kHz, thus having a low pass at 80 kHz is not a problem. When the oscillator reaches 20 kHz, the fourth harmonic (80 kHz) is partially attenuated, resulting in a lower reading from the voltmeter. When evaluating THD + N curves from any manufacturer, careful attention should be paid to the test conditions. The difference between an 80 kHz low-pass filter and a 500 kHz filter is shown in Figure 39. 0.01 ADA4627-1 TA = 25°C VSY = ±15V VIN = 810mV RL = 600Ω THD + N (%) 0.001 500kHz FILTER 0.0001 07559-017 80kHz FILTER 0.00001 0.01 0.1 1 FREQUENCY (kHz) 10 100 Figure 39. THD + N vs. Frequency PRINTED CIRCUIT BOARD LAYOUT, BIAS CURRENT, AND BYPASSING To take advantage of the very low input bias current of the ADA4627-1 at room temperature, leakage paths must be considered. A printed circuit board, with dust and humidity, can have 100 MΩ of resistance over a few tenths of an inch. A one mV differential between the two points results in 10 pA of leakage current, more than the guaranteed maximum. The op amp inputs should be guarded by surrounding the nets with a metal trace maintained at the predicted voltage. In the case of an inverting configuration or transimpedance amplifier, (see Figure 40), the inverting and noninverting nodes can be surrounded by traces held at a quiet analog ground. CF GUARD RF 2 ADA4627-1 3 8 6 + VOUT – 07559-053 IN For a noninverting configuration, the trace can be driven from the feedback divider, but the resistors should be chosen to offer a low impedance drive to the trace (see Figure 41). GUARD 3 ADA4627-1 + VS 2 8 6 VOUT + RF – RI – 07559-054 oscillator is connected to the circuit under test, and the output of the circuit goes back to the analyzer. Figure 41. Noninverting Amplifier with Guard The board layout should be compact with traces as short as possible. For second-order board considerations, such as triboelectric effects and piezoelectric effects, as well as a table of insulating material properties, see the AD549 data sheet. In some cases, shielding from air currents, may be helpful. A general rule of thumb, for op amps with gain bandwidth products higher than 1 MHz, bypass capacitors should be very close to the part, within 3 millimeters. Each supply should be bypassed with a 0.01 μF ceramic capacitor in parallel with a 1 μF bulk decoupling capacitor. The ceramic capacitors should be closer to the op amp. Sockets, which add inductance and capacitance, should not be used. OUTPUT PHASE REVERSAL Output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded. As common-mode voltage is moved outside the common-mode range, the outputs of these amplifiers can suddenly jump in the opposite direction to the supply rail. This is the result of the differential input pair shutting down, causing a radical shifting of internal voltages that results in the erratic output behavior. The ADA4627-1 amplifier has been carefully designed to prevent any output phase reversal if both inputs are maintained within the specified input voltage range. If one or both inputs exceed the input voltage range but remain within the supply rails, an internal loop opens and the output varies. Therefore, the inputs should always be a minimum of 3 V away from either supply rail. DRIVING CAPACITIVE LOADS Adding capacitance to the output of any op amp results in additional phase shift, which reduces stability and leads to overshoot or oscillation. The ADA4627-1 has a high phase margin and low output impedance, so it can drive reasonable values of capacitance. This is a common situation when an amplifier is used to drive the input of switched capacitor ADCs. For other considerations and various circuit solutions, see the Analog Dialogue article titled Ask the Applications Engineer-25, Op Amps Driving Capacitive Loads, available at www.analog.com. Figure 40. Inverting Amplifier with Guard Rev. A | Page 13 of 16 ADA4627-1 OUTLINE DIMENSIONS 0.60 MAX 5 2.95 2.75 SQ 2.55 TOP VIEW PIN 1 INDICATOR 8 12° MAX 0.05 MAX 0.01 NOM 0.30 0.23 0.18 SEATING PLANE 1 0.50 0.40 0.30 0.70 MAX 0.65 TYP 1.60 1.45 1.30 EXPOSED PAD (BOTTOM VIEW) 4 0.90 MAX 0.85 NOM 0.50 BSC 0.60 MAX 0.20 REF 1.89 1.74 1.59 PIN 1 INDICATOR FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. 090308-B 3.25 3.00 SQ 2.75 Figure 42. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD] 3 mm × 3 mm Body, Very Thin, Dual Lead (CP-8-2) Dimensions shown in millimeters 5.00 (0.1968) 4.80 (0.1890) 8 1 5 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 0.50 (0.0196) 0.25 (0.0099) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-A A CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 43. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) Rev. A | Page 14 of 16 012407-A 4.00 (0.1574) 3.80 (0.1497) ADA4627-1 ORDERING GUIDE Model ADA4627-1ACPZ-R2 1 ADA4627-1ACPZ-RL1 ADA4627-1ACPZ-R71 ADA4627-1ARZ1 ADA4627-1ARZ-RL1 ADA4627-1ARZ-R71 ADA4627-1BRZ1 ADA4627-1BRZ-R71 ADA4627-1BRZ-RL1 1 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C Package Description 8 Lead LFCSP_VD 8 Lead LFCSP_VD 8 Lead LFCSP_VD 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N Z = RoHS Compliant Part. Rev. A | Page 15 of 16 Package Option CP-8-2 CP-8-2 CP-8-2 R-8 R-8 R-8 R-8 R-8 R-8 Branding A29 A29 A29 ADA4627-1 NOTES ©2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07559-0-9/09(A) Rev. A | Page 16 of 16