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| (R) OPA 235 3 OPA 435 3 OPA 43 53 For most current data sheet and other product information, visit www.burr-brown.com OPA353 OPA2353 OPA4353 High-Speed, Single-Supply, Rail-to-Rail OPERATIONAL AMPLIFIERS MicroAmplifier TM Series FEATURES q q q q q q q q q RAIL-TO-RAIL INPUT RAIL-TO-RAIL OUTPUT (within 10mV) WIDE BANDWIDTH: 44MHz HIGH SLEW RATE: 22V/s LOW NOISE: 5nV/Hz LOW THD+NOISE: 0.0006% UNITY-GAIN STABLE MicroSIZE PACKAGES SINGLE, DUAL, AND QUAD APPLICATIONS q CELL PHONE PA CONTROL LOOPS q DRIVING A/D CONVERTERS q VIDEO PROCESSING q DATA ACQUISITION q PROCESS CONTROL q AUDIO PROCESSING q COMMUNICATIONS q ACTIVE FILTERS q TEST EQUIPMENT DESCRIPTION OPA353 series rail-to-rail CMOS operational amplifiers are designed for low cost, miniature applications. They are optimized for low voltage, single-supply operation. Rail-to-rail input/output, low noise (5nV/Hz), and high speed operation (44MHz, 22V/s) make them ideal for driving sampling analog-to-digital converters. They are also well suited for cell phone PA control loops and video processing (75 drive capability) as well as audio and general purpose applications. Single, dual, and quad versions have identical specifications for design flexibility. The OPA353 series operates on a single supply as low as 2.5V with an input common-mode voltage range that SPICE Model available at www.burr-brown.com OPA353 NC -In +In OPA353 Out 1 V- 2 +In 3 SOT-23-5 4 -In 5 Out A 1 2 A +In A +V 3 4 5 B -In B Out B NC 6 7 8 SSOP-16 C 11 10 9 -In C Out C NC D 14 13 12 +In D -V +In C extends 300mV beyond the supply rails. Output voltage swing is to within 10mV of the supply rails with a 10k load. Dual and quad designs feature completely independent circuitry for lowest crosstalk and freedom from interaction. The single (OPA353) packages are the tiny 5-lead SOT23-5 surface mount and SO-8 surface mount. The dual (OPA2353) comes in the miniature MSOP-8 surface mount and SO-8 surface mount. The quad (OPA4353) packages are the space-saving SSOP-16 surface mount and SO-14 surface mount. All are specified from -40C to +85C and operate from -55C to +125C. OPA4353 16 15 Out D -In D 1 2 3 4 SO-8 8 7 6 5 NC V+ Output NC Out A 1 2 3 4 SO-8, MSOP-8 A B 8 7 6 5 V+ Out B -In B +In B -In A +In A V- OPA2353 -In A V- +In B V+ (SO-14 package not shown) International Airport Industrial Park * Mailing Address: PO Box 11400, Tucson, AZ 85734 * Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 * Tel: (520) 746-1111 Twx: 910-952-1111 * Internet: http://www.burr-brown.com/ * Cable: BBRCORP * Telex: 066-6491 * FAX: (520) 889-1510 * Immediate Product Info: (800) 548-6132 (c) 1998 Burr-Brown Corporation PDS-1479B Printed in U.S.A. March, 1999 SBOS103 SPECIFICATIONS: VS = 2.7V to 5.5V At TA = +25C, RL = 1k connected to VS /2 and VOUT = VS /2, unless otherwise noted. Boldface limits apply over the specified temperature range, TA = -40C to +85C. VS = 5V. OPA353NA, UA OPA2353EA, UA OPA4353EA, UA PARAMETER OFFSET VOLTAGE Input Offset Voltage TA = -40C to +85C vs Temperature vs Power Supply Rejection Ratio TA = -40C to +85C Channel Separation (dual, quad) INPUT BIAS CURRENT Input Bias Current TA = -40C to +85C Input Offset Current NOISE Input Voltage Noise, f = 100Hz to 400kHz Input Voltage Noise Density, f = 10kHz f = 100kHz Current Noise Density, f = 10kHz INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection Ratio TA = -40C to +85C INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain TA = -40C to +85C TA = -40C to +85C FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate Settling Time, 0.1% 0.01% Overload Recovery Time Total Harmonic Distortion + Noise Differential Gain Error Differential Phase Error OUTPUT Voltage Output Swing from Rail(4) TA = -40C to +85C TA = -40C to +85C Output Current Short-Circuit Current Capacitive Load Drive POWER SUPPLY Operating Voltage Range Minimum Operating Voltage Quiescent Current (per amplifier) TA = -40C to +85C TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance SOT-23-5 MSOP-8 Surface Mount SO-8 Surface Mount SSOP-16 Surface Mount SO-14 Surface Mount GBW SR AOL RL = 10k, 50mV < VO < (V+) - 50mV RL = 10k, 50mV < VO < (V+) - 50mV RL = 1k, 200mV < VO < (V+) - 200mV RL = 1k, 200mV < VO < (V+) - 200mV CL = 100pF G=1 G=1 G = 1, 2V Step G = 1, 2V Step VIN * G = VS RL = 600, VO = 2.5Vp-p(2), G = 1, f = 1kHz G = 2, RL = 600, VO = 1.4V (3) G = 2, RL = 600, VO = 1.4V (3) RL = 10k, AOL 100dB RL = 10k, AOL 100dB RL = 1k, AOL 100dB RL = 1k, AOL 100dB 100 100 100 100 VOS CONDITION VS = 5V TA = -40C to +85C VS = 2.7V to 5.5V, VCM = 0V VS = 2.7V to 5.5V, VCM = 0V dc MIN TYP(1) 3 MAX 8 UNITS mV mV V/C V/V V/V V/V pA pA Vrms nV/Hz nV/Hz fA/Hz (V+) + 0.1 86 74 V dB dB dB || pF || pF dB dB dB dB MHz V/s s s s % % deg 50 50 200 200 mV mV mV mV mA mA 5 40 0.15 0.5 See Typical Curve 0.5 4 7 5 4 -0.1 76 60 58 10 150 175 PSRR IB I OS 10 10 en in VCM CMRR -0.1V < VCM < (V+) - 2.4V VS = 5V, -0.1V < VCM < 5.1V VS = 5V, -0.1V < VCM < 5.1V 1013 || 2.5 1013 || 6.5 122 120 THD+N 44 22 0.22 0.5 0.1 0.0006 0.17 0.17 10 25 40(5) 80 See Typical Curve 2.7 2.5 5.2 5.5 8 9 +85 +125 +125 200 150 150 100 100 VOUT I OUT I SC CLOAD VS IQ TA = -40C to +85C IO = 0 IO = 0 -40 -55 -55 V V mA mA C C C C/W C/W C/W C/W C/W JA NOTES: (1) VS = +5V. (2) VOUT = 0.25V to 2.75V. (3) NTSC signal generator used. See Figure 6 for test circuit. (4) Output voltage swings are measured between the output and power supply rails. (5) See typical performance curve, "Output Voltage Swing vs Output Swing." (R) OPA353, 2353, 4353 2 PIN CONFIGURATION Top View OPA4353 Out A -In A +In A V+ +In B -In B Out B 1 2 A 3 4 5 B 6 7 C 9 8 -In C Out C D 12 11 10 +In D V- +In C 14 13 Out D -In D SO-14 ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage ................................................................................... 5.5V Signal Input Terminals, Voltage(2) .................. (V-) - 0.3V to (V+) + 0.3V Current(2) .................................................... 10mA Output Short-Circuit(3) .............................................................. Continuous Operating Temperature .................................................. -55C to +125C Storage Temperature ..................................................... -55C to +125C Junction Temperature ...................................................................... 150C Lead Temperature (soldering, 10s) ................................................. 300C NOTES: (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. (2) Input terminals are diode-clamped to the power supply rails. Input signals that can swing more than 0.3V beyond the supply rails should be current-limited to 10mA or less. (3) Short circuit to ground, one amplifier per package. PACKAGE/ORDERING INFORMATION PACKAGE DRAWING NUMBER(1) SPECIFIED TEMPERATURE RANGE PACKAGE MARKING ORDERING NUMBER(2) TRANSPORT MEDIA PRODUCT Single OPA353NA PACKAGE 5-Lead SOT-23-5 331 -40C to +85C D53 " OPA353UA " SO-8 Surface Mount " 182 " -40C to +85C " OPA353UA " Dual OPA2353EA " MSOP-8 Surface Mount " 337 " -40C to +85C " E53 OPA353NA /250 OPA353NA /3K OPA353UA OPA353UA /2K5 Tape and Reel Tape and Reel Rails Tape and Reel " OPA2353UA " SO-8 Surface Mount " 182 " -40C to +85C " OPA2353UA " Quad OPA4353EA " SSOP-16 Surface Mount " 322 " -40C to +85C " OPA4353EA OPA2353EA /250 OPA2353EA/2K5 OPA2353UA OPA2353UA/2K5 Tape and Reel Tape and Reel Rails Tape and Reel " OPA4353UA " SO-14 Surface Mount " 235 " -40C to +85C " OPA4353UA " " " " " OPA4353EA /250 OPA4353EA/2K5 OPA4353UA OPA4353UA/2K5 Tape and Reel Tape and Reel Rails Tape and Reel NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of "OPA2353EA/2K5" will get a single 2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. (R) 3 OPA353, 2353, 4353 TYPICAL PERFORMANCE CURVES At TA = +25C, VS = +5V, and RL = 1k connected to VS/2, unless otherwise noted. OPEN-LOOP GAIN/PHASE vs FREQUENCY 160 140 120 Voltage Gain (dB) POWER SUPPLY AND COMMON-MODE REJECTION RATIO vs FREQUENCY 0 100 90 PSRR -45 PSRR, CMRR (dB) 80 70 60 50 40 30 20 10 CMRR (VS = +5V VCM = -0.1V to 5.1V) 80 60 G 40 20 0 0.1 1 10 100 1k 10k -90 -135 -180 100k 1M 10M 100M Frequency (Hz) Phase () 100 0 10 100 1k 10k 100k 1M 10M Frequency (Hz) INPUT VOLTAGE AND CURRENT NOISE SPECTRAL DENSITY vs FREQUENCY 100k 10k CHANNEL SEPARATION vs FREQUENCY 140 130 Channel Separation (dB) 10k Voltage Noise (nVHz) Current Noise 1k Current Noise (fAHz) 120 110 100 90 80 70 Dual and Quad Versions 10 100 1k 10k 100k 1M 10M 1k Voltage Noise 100 100 10 10 1 1 10 100 1k 10k 100k 1M Frequency (Hz) 0.1 10M 60 Frequency (Hz) TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 1 RL = 600 Harmonic Distortion (%) HARMONIC DISTORTION + NOISE vs FREQUENCY 1 (-40dBc) 0.1 (-60dBc) 0.01 (-80dBc) 0.001 (-100dBc) 0.0001 (-120dBc) 1k G=1 VO = 2.5Vp-p RL = 600 0.1 G = 100, 3Vp-p (VO = 1V to 4V) THD+N (%) 0.01 G = 10, 3Vp-p (VO = 1V to 4V) G = 1, 3Vp-p (VO = 1V to 4V) Input goes through transition region G = 1, 2.5Vp-p (VO = 0.25V to 2.75V) Input does NOT go through transition region 0.001 3rd Harmonic 2nd Harmonic 10k 100k Frequency (Hz) 1M 0.0001 10 100 1k Frequency (Hz) 10k 100k (R) OPA353, 2353, 4353 4 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = +5V, and RL = 1k connected to VS/2, unless otherwise noted. DIFFERENTIAL GAIN/PHASE vs RESISTIVE LOAD 0.5 Phase G=2 VO = 1.4V NTSC Signal Generator See Figure 6 for test circuit. OPEN-LOOP GAIN vs TEMPERATURE 130 0.4 Differential Gain (%) Differential Phase () 0.3 Open-Loop Gain (dB) 125 RL = 10k RL = 1k 120 RL = 600 115 0.2 Gain 0.1 0 0 100 200 300 400 500 600 700 800 900 1000 Resistive Load () 110 -75 -50 -25 0 25 50 75 100 125 Temperature (C) COMMON-MODE AND POWER SUPPLY REJECTION RATIO vs TEMPERATURE 90 110 SLEW RATE vs TEMPERATURE 40 35 80 Slew Rate (V/s) CMRR, VS = 5V (VCM = -0.1V to +5.1V) 100 30 PSRR (dB) Negative Slew Rate Positive Slew Rate CMRR (dB) 25 20 15 10 5 70 PSRR 60 90 80 50 -75 70 -50 -25 0 25 50 75 100 125 Temperature (C) 0 -75 -50 -25 0 25 50 75 100 125 Temperature (C) QUIESCENT CURRENT AND SHORT-CIRCUIT CURRENT vs TEMPERATURE 7.0 +ISC 6.5 90 100 QUIESCENT CURRENT vs SUPPLY VOLTAGE 6.0 Per Amplifier Short-Circuit Current (mA) 5.5 Quiescent Current (mA) Quiescent Current (mA) 6.0 5.5 5.0 4.5 4.0 3.5 -75 -ISC 80 70 IQ 60 50 40 30 5.0 4.5 4.0 3.5 3.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Supply Voltage (V) -50 -25 0 25 50 75 100 125 Temperature (C) (R) 5 OPA353, 2353, 4353 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = +5V, and RL = 1k connected to VS/2, unless otherwise noted. INPUT BIAS CURRENT vs TEMPERATURE 1k 1.5 INPUT BIAS CURRENT vs INPUT COMMON-MODE VOLTAGE Input Bias Current (pA) 10 Input Bias Current (pA) -75 -50 -25 0 25 50 Temperature (C) 75 100 125 100 1.0 0.5 1 0.0 0.1 -0.5 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Common-Mode Voltage (V) CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY 100 10 6 5 MAXIMUM OUTPUT VOLTAGE vs FREQUENCY VS = 5.5V Maximum output voltage without slew rate-induced distortion. Output Impedance () Output Voltage (Vp-p) 1 0.1 0.01 0.001 0.0001 1 10 100 1k 10k 100k 1M 10M 100M Frequency (Hz) G = 100 G = 10 G=1 4 3 2 1 0 100k VS = 2.7V 1M Frequency (Hz) 10M 100M OUTPUT VOLTAGE SWING vs OUTPUT CURRENT V+ 140 130 OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING IOUT = 250A IOUT = 2.5mA (V+)-1 Output Voltage (V) +125C (V+)-2 Open-Loop Gain (dB) -55C +25C 120 110 100 90 80 70 IOUT = 4.2mA (V-)+2 Depending on circuit configuration (including closed-loop gain) performance may be degraded in shaded region. +125C +25C -55C (V-)+1 (V-) 0 60 10 20 Output Current (mA) 30 40 0 20 40 60 80 100 120 140 160 180 200 Output Voltage Swing from Supply Rails (mV) (R) OPA353, 2353, 4353 6 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25C, VS = +5V, and RL = 1k connected to VS/2, unless otherwise noted. OFFSET VOLTAGE PRODUCTION DISTRIBUTION 25 35 OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION Typical production distribution of packaged units. Percent of Amplifiers (%) 20 Percent of Units (%) Typical production distribution of packaged units. 30 25 20 15 10 5 0 15 10 5 0 -8 -7 -6 -5 4 -3 -2 -1 0 1 2 3 4 5 6 78 Offset Voltage (mV) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Offset Voltage Drift (V/C) SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE 80 70 G=1 50 G = -1 40 30 20 10 0 10 100 1k 10k 100k 1M Load Capacitance (pF) G = 10 SETTLING TIME vs CLOSED-LOOP GAIN 10 Settling Time (s) 60 0.01% Overshoot (%) 1 0.1% 0.1 1 10 Closed-Loop Gain (V/V) 100 SMALL-SIGNAL STEP RESPONSE CL = 100pF LARGE-SIGNAL STEP RESPONSE CL = 100pF 50mV/div 1V/div 100ns/div 200ns/div (R) 7 OPA353, 2353, 4353 APPLICATIONS INFORMATION OPA353 series op amps are fabricated on a state-of-the-art 0.6 micron CMOS process. They are unity-gain stable and suitable for a wide range of general purpose applications. Rail-to-rail input/output make them ideal for driving sampling A/D converters. They are well suited for controlling the output power in cell phones. These applications often require high speed and low noise. In addition, the OPA353 series offers a low cost solution for general purpose and consumer video applications (75 drive capability). Excellent ac performance makes the OPA353 series well suited for audio applications. Their bandwidth, slew rate, low noise (5nV/Hz), low THD (0.0006%), and small package options are ideal for these applications. The class AB output stage is capable of driving 600 loads connected to any point between V+ and ground. Rail-to-rail input and output swing significantly increases dynamic range, especially in low voltage supply applications. Figure 1 shows the input and output waveforms for VS = +5, G = +1, RL = 1k 5V the OPA353 in unity-gain configuration. Operation is from a single +5V supply with a 1k load connected to VS /2. The input is a 5Vp-p sinusoid. Output voltage is approximately 4.95Vp-p. Power supply pins should be bypassed with 0.01F ceramic capacitors. OPERATING VOLTAGE OPA353 series op amps are fully specified from +2.7V to +5.5V. However, supply voltage may range from +2.5V to +5.5V. Parameters are guaranteed over the specified supply range--a unique feature of the OPA353 series. In addition, many specifications apply from -40C to +85C. Most behavior remains virtually unchanged throughout the full operating voltage range. Parameters which vary significantly with operating voltages or temperature are shown in the typical performance curves. RAIL-TO-RAIL INPUT The guaranteed input common-mode voltage range of the OPA353 series extends 100mV beyond the supply rails. This is achieved with a complementary input stage--an N-channel input differential pair in parallel with a P-channel differential pair (see Figure 2). The N-channel pair is active for input voltages close to the positive rail, typically (V+) - 1.8V to 100mV above the positive supply, while the P-channel pair is on for inputs from 100mV below the negative supply to approximately (V+) - 1.8V. There is a small transition region, typically (V+) - 2V to (V+) - 1.6V, in which both pairs are on. This 400mV transition region can vary 400mV with process variation. Thus, the transition region (both input stages on) can range from (V+) - 2.4V to (V+) - 2.0V on the low end, up to (V+) - 1.6V to (V+) - 1.2V on the high end. VIN 1.25V/div V+ Reference Current VIN+ VIN- 0 5V VOUT 0 FIGURE 1. Rail-to-Rail Input and Output. VBIAS1 Class AB Control Circuitry VO VBIAS2 V- (Ground) FIGURE 2. Simplified Schematic. (R) OPA353, 2353, 4353 8 A double-folded cascode adds the signal from the two input pairs and presents a differential signal to the class AB output stage. Normally, input bias current is approximately 500fA. However, large inputs (greater than 300mV beyond the supply rails) can turn on the OPA353's input protection diodes, causing excessive current to flow in or out of the input pins. Momentary voltages greater than 300mV beyond the power supply can be tolerated if the current on the input pins is limited to 10mA. This is easily accomplished with an input resistor as shown in Figure 3. Many input signals are inherently current-limited to less than 10mA, therefore, a limiting resistor is not required. FEEDBACK CAPACITOR IMPROVES RESPONSE For optimum settling time and stability with high-impedance feedback networks, it may be necessary to add a feedback capacitor across the feedback resistor, RF, as shown in Figure 4. This capacitor compensates for the zero created by the feedback network impedance and the OPA353's input capacitance (and any parasitic layout capacitance). The effect becomes more significant with higher impedance networks. CF RIN VIN RF V+ IOVERLOAD 10mA max VIN 5k V+ OPAx353 VOUT RIN * CIN = RF * CF CIN OPA353 CL CIN VOUT FIGURE 3. Input Current Protection for Voltages Exceeding the Supply Voltage. RAIL-TO-RAIL OUTPUT A class AB output stage with common-source transistors is used to achieve rail-to-rail output. For light resistive loads (>10k), the output voltage swing is typically ten millivolts from the supply rails. With heavier resistive loads (600 to 10k), the output can swing to within a few tens of millivolts from the supply rails and maintain high open-loop gain. See the typical performance curves "Output Voltage Swing vs Output Current" and "Open-Loop Gain vs Output Voltage." CAPACITIVE LOAD AND STABILITY OPA353 series op amps can drive a wide range of capacitive loads. However, all op amps under certain conditions may become unstable. Op amp configuration, gain, and load value are just a few of the factors to consider when determining stability. An op amp in unity gain configuration is the most susceptible to the effects of capacitive load. The capacitive load reacts with the op amp's output impedance, along with any additional load resistance, to create a pole in the small-signal response which degrades the phase margin. In unity gain, OPA353 series op amps perform well with large capacitive loads. Increasing gain enhances the amplifier's ability to drive more capacitance. The typical performance curve "Small-Signal Overshoot vs Capacitive Load" shows performance with a 1k resistive load. Increasing load resistance improves capacitive load drive capability. Where CIN is equal to the OPA353's input capacitance (approximately 9pF) plus any parastic layout capacitance. FIGURE 4. Feedback Capacitor Improves Dynamic Performance. It is suggested that a variable capacitor be used for the feedback capacitor since input capacitance may vary between op amps and layout capacitance is difficult to determine. For the circuit shown in Figure 4, the value of the variable feedback capacitor should be chosen so that the input resistance times the input capacitance of the OPA353 (typically 9pF) plus the estimated parasitic layout capacitance equals the feedback capacitor times the feedback resistor: RIN * CIN = RF * CF where CIN is equal to the OPA353's input capacitance (sum of differential and common-mode) plus the layout capacitance. The capacitor can be varied until optimum performance is obtained. DRIVING A/D CONVERTERS OPA353 series op amps are optimized for driving medium speed (up to 500kHz) sampling A/D converters. However, they also offer excellent performance for higher speed converters. The OPA353 series provides an effective means of buffering the A/D's input capacitance and resulting charge injection while providing signal gain. For applications requiring high accuracy, the OPA350 series is recommended. (R) 9 OPA353, 2353, 4353 Figure 5 shows the OPA353 driving an ADS7861. The ADS7861 is a dual, 12-bit, 500kHz sampling converter in the small SSOP-24 package. When used with the miniature package options of the OPA353 series, the combination is ideal for space-limited and low power applications. For further information consult the ADS7861 data sheet. OUTPUT IMPEDANCE The low frequency open-loop output impedance of the OPA353's common-source output stage is approximately 1k. When the op amp is connected with feedback, this value is reduced significantly by the loop gain of the op amp. For example, with 122dB of open-loop gain, the output impedance is reduced in unity-gain to less than 0.001. For each decade rise in the closed-loop gain, the loop gain is reduced by the same amount which results in a ten-fold increase in output impedance (see the typical performance curve, "Output Impedance vs Frequency"). At higher frequencies, the output impedance will rise as the open-loop gain of the op amp drops. However, at these frequencies the output also becomes capacitive due to parasitic capacitance. This prevents the output impedance from becoming too high, which can cause stability problems when driving capacitive loads. As mentioned previously, the OPA353 has excellent capacitive load drive capability for an op amp with its bandwidth. VIDEO LINE DRIVER Figure 6 shows a circuit for a single supply, G = 2 composite video line driver. The synchronized outputs of a composite video line driver extend below ground. As shown, the input to the op amp should be ac-coupled and shifted positively to provide adequate signal swing to account for these negative signals in a single-supply configuration. The input is terminated with a 75 resistor and ac-coupled with a 47F capacitor to a voltage divider that provides the dc bias point to the input. In Figure 6, this point is approximately (V-) + 1.7V. Setting the optimal bias point requires some understanding of the nature of composite video signals. For best performance, one should be careful to avoid the distortion caused by the transition region of the OPA353's complementary input stage. Refer to the discussion of rail-to-rail input. CB1 2k +5V 2k 2 VIN B1 4 1/4 3 OPA4353 0.1F 0.1F CB0 24 2k 2k 2 6 1/4 5 OPA4353 7 3 4 5 6 7 2k 2k 8 9 9 1/4 10 OPA4353 8 10 11 CH B1+ CH B1- CH B0+ CH B0- CH A1+ +VD 13 +VA Serial Data A Serial Data B BUSY CLOCK CS 23 22 21 20 19 18 17 16 15 14 Serial Interface VIN B0 CA1 ADS7861 CH A1- CH A0+ CH A0- REFIN REFOUT DGND 1 AGND 12 RD CONVST A0 M0 M1 VIN A1 CA0 2k 2k 1/4 OPA4353 VIN A0 11 14 VIN = 0V to 2.45V for 0V to 4.9V output. Choose CB1, CB0, CA1, CA0 to filter high frequency noise. FIGURE 5. OPA4353 Driving Sampling A/D Converter. (R) OPA353, 2353, 4353 10 RG 1k C1 220F +5V RF 1k C4 0.1F 0.1F 7 + 10F C2 47F Video In R1 75 R2 5k OPA353 4 R3 5k R4 5k C3 10F 6 C5 1000F ROUT Cable VOUT RL +5V (pin 7) FIGURE 6. Single-Supply Video Line Driver. +5V 50k (2.5V) 8 RG REF1004-2.5 4 +5V R3 25k R4 100k R1 100k R2 25k 1/2 OPA2353 1/2 OPA2353 200k RG RL 10k VOUT G=5+ FIGURE 7. Two Op-Amp Instrumentation Amplifier With Improved High Frequency Common-Mode Rejection. <1pF (prevents gain peaking) 10M +V OPA353 VO R1 10.5k +2.5V C1 1830pF VIN C2 270pF OPA353 RL 20k -2.5V VOUT FIGURE 8. Transimpedance Amplifier. C1 4.7F +2.5V R2 49.9k FIGURE 10. 10kHz High-Pass Filter. R1 2.74k VIN C2 1nF -2.5V R2 19.6k OPA353 RL 20k VOUT FIGURE 9. 10kHz Low-Pass Filter. (R) 11 OPA353, 2353, 4353 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI's publication of information regarding any third party's products or services does not constitute TI's approval, warranty or endorsement thereof. Copyright (c) 2000, Texas Instruments Incorporated |
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