OPA2725AIDGKT

OPA725, OPA2725 OPA726, OPA2726 SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 Very Low Noise, High-Speed, 12V CMOS Operational Amplifier FEATURES D D D D D D D D D D D D D D D D D D D D BANDWIDTH: 20MHz SLEW RATE: 30V/µs FAST 16-BIT SETTLING TIME LOW NOISE: 6nV/√Hz (typ) at 100kHz EXCELLENT CMRR, PSRR, and AOL RAIL-TO-RAIL OUTPUT CM RANGE INCLUDES GND THD+N: 0.0003% (typ) at 1kHz QUIESCENT CURRENT: 5.5mA/ch (max) SUPPLY VOLTAGE: 4V to 12V SHUTDOWN MODE (OPAx726): 6µA/ch DESCRIPTION The OPA725 and OPA726 series op amps use a state-of-the-art 12V analog CMOS process, and combine outstanding ac performance with low bias current and excellent CMRR, PSRR, and AOL. The 20MHz Gain-Bandwidth (GBW) Product is achieved by using a proprietary and patent-pending output stage design. These characteristics allow excellent 16-bit settling times for driving 16-bit Analog-to-Digital converters (ADCs). Excellent ac characteristics, such as 20MHz GBW, 30V/µs slew rate and 0.0003% THD+N make the OPA725 and OPA726 well-suited for communication, high-end audio, and active filter applications. With a bias current of less than 200pA, they are well-suited for use as transimpedance (I/V-conversion) amplifiers for monitoring optical power in ONET applications. The OPA725 and OPA726 op amps can be used in single-supply applications from 4V up to 12V, or dual-supply from ±2V to ±6V. The output swings to within 150mV of the rails, maximizing dynamic range. The shutdown versions (OPAx726) reduce the quiescent current to less than 6µA and feature a reference pin for easy shutdown operation with standard CMOS logic in dual-supply applications. The OPA725 (single) is available in SOT23-5 and SO-8 packages, and the OPA2725 (dual) is available in MSOP-8 and SO-8 packages. The OPA726 (single with shutdown) is available in MSOP-8 and SO-8. The OPA2726 (dual with shutdown) is available in MSOP-10. All versions are specified for operation from −40°C to +125°C. APPLICATIONS OPTICAL NETWORKING TRANSIMPEDANCE AMPLIFIERS INTEGRATORS ACTIVE FILTERS A/D CONVERTER BUFFERS I/V CONVERTER FOR DACs PORTABLE AUDIO PROCESS CONTROL TEST EQUIPMENT OPA725 RELATED PRODUCTS FEATURES 10MHz, 16V, 16V/µs, 8.5nV/√Hz at 1kHz 8MHz, 36V, FET Input, 20V/µs, 8.5nV/√Hz at 1kHz 100MHz, 5.5V, Precision Transimpedance Amplifier 500MHz, ±5V, FET Input, 290V/µs, 7nV/√Hz at 100kHz 7MHz, 12V, RRIO, 10V/µs, 30nV/√Hz at 10kHz 16-Bit, 250kSPS, 4-Channel, Parallel Output ADC PRODUCT TLC080 OPA132 OPA380 OPA656 OPA743 ADS8342 +5V +12V 75Ω λ O PA726 +5V VOUT VIN ± 2.5V OPA725 AIN ADS8342 330pF − 5V 16− ADC Bit Common Enable − VB − 5V Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright  2003−2004, Texas Instruments Incorporated www.ti.com OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 ORDERING INFORMATION PRODUCT Non-Shutdown OPA725 ″ OPA725 ″ OPA2725 ″ OPA2725 ″ Shutdown OPA726 ″ OPA726 ″ OPA2726 ″ SO-8 ″ MSOP-8 ″ MSOP-10 ″ D ″ DGK ″ DGS ″ −40°C to +125°C ″ −40°C to +125°C ″ −40°C to +125°C ″ OPA726A ″ BHC ″ BHB ″ OPA726AID OPA726AIDR OPA726AIDGKT OPA726AIDGKR OPA2726AIDGST OPA2726AIDGSR Rails, 100 Tape and Reel, 2500 Tape and Reel, 250 Tape and Reel, 2500 Tape and Reel, 250 Tape and Reel, 2500 SOT23-5 ″ SO-8 ″ SO-8 ″ MSOP-8 ″ DBV ″ D ″ D ″ DGK ″ −40°C to +125°C ″ −40°C to +125°C ″ −40°C to +125°C ″ −40°C to +125°C ″ OALI ″ OPA725A ″ OPA2725A ″ BGM ″ OPA725AIDBVT OPA725AIDBVR OPA725AID OPA725AIDR OPA2725AID OPA2725AIDR OPA2725AIDGKT OPA2725AIDGKR Tape and Reel, 250 Tape and Reel, 3000 Rails, 100 Tape and Reel, 2500 Rails, 100 Tape and Reel, 2500 Tape and Reel, 250 Tape and Reel, 2500 PACKAGE-LEAD PACKAGE DESIGNATOR(1) SPECIFIED TEMPERATURE RANGE PACKAGE MARKING ORDERING NUMBER TRANSPORT MEDIA, QUANTITY (1) For the most current package and ordering information, see the Package Option Addendum located at the end of this datasheet. This integrated circuit can be damaged by ESD. Texas Instruments 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +13.2V Signal Input Terminals, Voltage(2) . . . . . . . . . −0.5V to (V+) + 0.5V Current(2) . . . . . . . . . . . . . . . . . . . ±10mA Output Short Circuit(3) . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Operating Temperature . . . . . . . . . . . . . . . . . . . . . −55°C to +125°C Storage Termperature . . . . . . . . . . . . . . . . . . . . . . −55°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . +300°C ESD Rating (Human Body Model) . . . . . . . . . . . . . . . . . . . . 1000 V (1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not supported. (2) Input terminals are diode-clamped to the power-supply rails. Input signals that can swing more than 0.5V beyond the supply rails should be current limited to 10mA or less. (3) Short-circuit to ground, one amplifier per package. 2 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 PIN CONFIGURATIONS OPA725 OPA725 NC(1) Out V− +IN 1 2 3 SOT23− 5 SO− 8 4 − IN +IN V− 3 4 6 5 OUT NC(1) +IN V− 3 4 5 V+ − IN 2 7 V+ − IN 2 1 8 NC(1) DGND(2) 1 OPA726 8 7 6 5 SO− MSOP− 8, 8 Enable V+ OUT NC(1) OPA2725 OUT A 1 A B 8 7 6 5 SO− MSOP− 8, 8 V+ OUT B − IN B +IN B OUT A 1 OPA2726 10 V+ A B 9 8 7 6 MSOP− 10 OUT B − IN B +IN B Enable − IN A 2 +IN A V− 3 4 − IN A 2 +IN A V− DGND(2) 3 4 5 (1) NC denotes no internal connection. (2) DGND = reference voltage for Enable Reference pin. Voltage on this pin will be the voltage to which the Enable Reference pin is referenced. 3 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 ELECTRICAL CHARACTERISTICS: VS = +4V to +12V or VS = ±2V to ±6V Boldface limits apply over the specified temperature range, TA = −40°C to +125°C. At TA = +25°C, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. OPA725, OPA726, OPA2725, OPA2726 PARAMETER OFFSET VOLTAGE Input Offset Voltage OPA725, OPA726 OPA2725, OPA2726 Drift vs Power Supply Over Temperature Channel Separation, DC INPUT BIAS CURRENT Input Bias Current Over Temperature Input Offset Current NOISE Input Voltage Noise, f = 0.1Hz to 10Hz Input Voltage Noise Density, f = 10kHz Input Voltage Noise Density, f = 100kHz Input Current Noise Density, f = 1kHz INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection Ratio Over Temperature Over Temperature INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain OPA725, OPA726 Over Temperature OPA2725, OPA2726 Over Temperature OPA725, OPA726 Over Temperature OPA2725, OPA2726 Over Temperature FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate Settling Time, 0.1% 0.01% Overload Recovery Time Total Harmonic Distortion + Noise AOL RL = 100kΩ, 0.15V < VO < (V+) − 0.15V RL = 100kΩ, 0.15V < VO < (V+) − 0.15V RL = 100kΩ, 0.175V < VO < (V+) − 0.175V RL = 100kΩ, 0.175V < VO < (V+) − 0.175V RL = 1kΩ, 0.25V < VO < (V+) − 0.25V RL = 1kΩ, 0.25V < VO < (V+) − 0.25V RL = 2kΩ, 0.25V < VO < (V+) − 0.25V RL = 2kΩ, 0.25V < VO < (V+) − 0.25V CL = 20pF GBW SR tS G = +1 VS = ±6V, 5V Step, G = +1 VS = ±6V, 5V Step, G = +1 VIN • Gain > VS VS = ±6V, VOUT = 2VRMS, RL = 600Ω, G = +1, f = 1kHz CONDITIONS VOS VS = ±6V, VCM = 0V VS = ±6V, VCM = 0V dVOS/dT PSRR VS = ±2V to ±6V, VCM = V− VS = ±2V to ±6V, VCM = V− MIN TYP MAX UNIT 1.2 1.5 4 30 1 3 5 100 150 mV mV µV/°C µV/V mV/V µV/V pA pA µVPP nV/√Hz nV/√Hz fA/√Hz IB IOS en en en in VCM CMRR VS = ±6V, VS = ±6V, VS = ±6V, VS = ±6V, VCM = 0V VCM = 0V VCM = 0V VCM = 0V 30 200 See Typical Characteristics 10 50 10 10 6 2.5 (V−) 88 84 94 84 (V+) − 2 94 100 (V−) ≤ VCM ≤ (V+) − 2V (V−) ≤ VCM ≤ (V+) − 2V (V−) ≤ VCM ≤ (V+) − 3V (V−) ≤ VCM ≤ (V+) − 3V V dB dB dB dB Ω pF Ω pF 1011 5 1011 4 110 100 110 100 106 96 106 96 120 120 116 116 dB dB dB dB dB dB dB dB MHz V/µs ns ns ns % THD+N 20 30 350 450 50 0.0003 4 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 ELECTRICAL CHARACTERISTICS: VS = +4V to +12V or VS = ±2V to ±6V (continued) Boldface limits apply over the specified temperature range, TA = −40°C to +125°C. At TA = +25°C, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. OPA725, OPA726, OPA2725, OPA2726 PARAMETER OUTPUT Voltage Output Swing from Rail OPA725, OPA726 Over Temperature OPA2725, OPA2726 Over Temperature OPA725, OPA726 Over Temperature OPA2725, OPA2726 Over Temperature Output Current Short-Circuit Current Capacitive Load Drive Open-Loop Output Impedance ENABLE/SHUTDOWN (OPAx726) tOFF tON Enable Reference (DGND) Voltage Range VL (shutdown) VH (amplifier is active) Input Disable Current IQSD (per amplifier) POWER SUPPLY Specified Voltage Range Operating Voltage Range Quiescent Current (per amplifier) Over Temperature TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance SOT23-5 MSOP-8, MSOP-10, SO-8 CONDITIONS MIN TYP MAX UNIT IOUT ISC CLOAD RL = 100kΩ, AOL > 110dB RL = 100kΩ, AOL > 100dB RL = 100kΩ, AOL > 110dB RL = 100kΩ, AOL > 100dB RL = 1kΩ, AOL > 106dB RL = 1kΩ, AOL > 96dB RL = 2kΩ, AOL > 106dB RL = 2kΩ, AOL > 96dB  VS − VOUT < 1V 100 125 200 200 150 150 175 175 250 250 250 250 f = 1MHz, IO = 0 40 ±55 See Typical Characteristics 40 5 30 mV mV mV mV mV mV mV mV mA mA Ω µs µs V V V µA µA V V mA mA °C °C °C °C/W °C/W VDGND V− > VDGND +2V Ref Pin = Enable Pin = V− 5 6 4 IO = 0 3.5 to 13.2 4.3 (V+) − 2 < VDGND +0.8V 15 12 5.5 6 125 125 150 VS VS IQ −40 −55 −55 qJA 200 150 5 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS At TA = +25°C, VS = ±6V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. GAIN AND PHASE vs FREQUENCY 180 160 140 120 Gain (dB) 100 80 60 40 20 0 − 20 10 100 1k 10k 100k 1M 10M Frequency (Hz) Gain Phase 180 160 140 120 100 80 60 40 20 0 −20 100M CMRR (dB) Phase (_ ) COMMON−MODE REJECTION RATIO vs FREQUENCY 120 100 80 60 40 20 (V− ) ≤ VCM ≤ (V+) − 2V 0 10 100 1k 10k 100k 1M 10M Frequency (Hz) POWER−SUPPLY REJECTION RATIO vs FREQUENCY 100 90 80 Amplitude (V) 70 PSRR (dB) 60 50 40 30 20 10 0 100 1k 10k 100k Frequency (Hz) 1M 10M 100M 0 10k 5 4 3 2 1 7 MAXIMUM OUTPUT VOLTAGE vs FREQUENCY VS = ± 6V 6 Indicates maximum output for no visible distortion. 100k Frequency (Hz) 1M 10M CHANNEL SEPARATION vs FREQUENCY 140 120 100 80 60 40 20 1k 10k 100k 1M 10M 100M 1 10 Voltage Noise (nV/√ Hz) 1000 INPUT VOLTAGE NOISE SPECTRAL DENSITY vs FREQUENCY Channel Separation (dB) 100 10 100 1k 10k 100k 1M 10M Frequency (Hz) Frequency (Hz) 6 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = ±6V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. INPUT BIAS CURRENT vs COMMON −MODE VOLTAGE 100k 10k Input Bias Current (pA) 1k 100 10 − 10 − 100 − 1k − 10k − 100k − 6.5 − 5.5 − 4.5 − 3.5 − 2.5 − 1.5 − 0.5 +25_ C +85_ C +125_ C 0.5 1.5 2.5 3.5 4.5 5.5 6.5 IB < ± 10pA +85_ C +25_ C IOS (pA) 100 10 1 0.1 0.01 − 50 − 25 +125_ C 1k 10k OFFSET CURRENT vs TEMPERATURE 0 25 50 75 100 125 150 Temperature (_ C) Common− Mode Voltage (V) OPEN−LOOP GAIN vs TEMPERATURE 140 130 120 AOL (dB) 110 100 90 80 − 50 60 0 25 50 75 100 125 150 Temperature (_ C) RL = 1kΩ 120 POWER−SUPPLY REJECTION RATIO vs TEMPERATURE RL = 100kΩ PSRR (dB) 100 80 − 25 − 50 − 25 0 25 50 75 100 125 150 Temperature (_ C) COMMON−MODE REJECTION RATIO vs TEMPERATURE 110 QUIESCENT CURRENT vs TEMPERATURE 5 100 CMRR (dB) 4 90 IQ (mA) 3 80 2 70 (V− ) ≤ VCM ≤ (V+) − 2V 60 − 50 − 25 0 25 1 0 50 75 100 125 150 − 50 − 25 0 25 50 75 100 125 150 Temperature (_ C) Temperature (_ C) 7 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = ±6V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. QUIESCENT CURRENT vs SUPPLY VOLTAGE 5.0 4.8 4.6 I Q per Amplifier (mA) 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 3 4 5 6 7 8 9 10 11 12 13 14 Supply Voltage (V) Short− Circuit (mA) SHORT−CIRCUIT CURRENT vs TEMPERATURE 90 80 70 60 50 Sinking 40 30 20 10 0 − 50 − 25 0 25 50 75 100 125 150 Sourcing Temperature (_ C) SHORT−CIRCUIT CURRENT vs SUPPLY VOLTAGE 90 80 Short− Circuit Current (mA) 70 60 50 40 30 20 10 0 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 −4 −6 0 Sinking Output Voltage (V) Sourcing 6 4 2 OUTPUT VOLTAGE SWING vs OUTPUT CURRENT − 40_ C 125_ C 0 −2 25_ C − 40_ C 10 20 30 40 50 60 70 80 Supply Voltage (V) Output Current (mA) TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY 0.01 RL = 600Ω VOUT = 2Vrms BW = 80kHz Settling Time (ns) SETTLING TIME vs GAIN 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0.1% 0.01% THD + Noise (%) 0.001 0.0001 10 100 1k Frequency (Hz) 10k 100k 0 1 10 Noninverting Gain (V/V) 100 8 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = ±6V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. SMALL−SIGNAL OVERSHOOT vs CAPACITIVE LOAD 90 80 70 Overshoot (%) G = +1 50 40 30 20 10 0 10 100 Capacitive Load (pF) 1000 G = +5 CF = 1pF G = −1 CF = 3pF Population 60 OFFSET VOLTAGE PRODUCTION DISTRIBUTION VOLTAGE OFFSET DRIFT PRODUCTION DISTRIBUTION Typical production distribution of packaged units. Population 0 2 4 6 8 10 12 14 16 10mV/div Voltage Offset Drift (µV/ _ C) LARGE−SIGNAL STEP RESPONSE G = +1 RL = 10kΩ CL = 20pF CF = 2pF 10mV/div 1V/div 400ns/div − 3.3 − 3.0 − 2.7 − 2.4 − 2.1 − 1.8 − 1.5 − 1.2 − 0.9 − 0.6 − 0.3 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 3.3 Offset Voltage (mV) SMALL−SIGNAL STEP RESPONSE G = +1 RL = 10kΩ CL = 20pF 100ns/div SMALL− SIGNAL STEP RESPONSE CF = 3pF CF = 4pF CF RF 10kΩ 10kΩ O P A 7 25 G = −1 CL 20pF 200ns/div 9 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = ±6V, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted. LARGE−SIGNAL STEP RESPONSE 1V/div CF 4pF RF 10kΩ 10k Ω OPA725 G = −1 CL 20pF 400ns/div 10 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 APPLICATIONS INFORMATION OPA725 and OPA726 series 20MHz CMOS op amps have a fast slew rate, low noise, and excellent PSRR, CMRR, and AOL. These op amps can operate on typically 4.3mA quiescent current from a single (or split) supply in the range of 4V to 12V (±2V to ±6V), making them highly versatile and easy to use. They are stable in a unity-gain configuration. Power-supply pins should be bypassed with 1nF ceramic capacitors in parallel with 1µF tantalum capacitors. a) Single− Supply Configuration Enable Digital Logic +12V OPA726 VOUT DGND OPERATING VOLTAGE OPA725 series op amps are specified from 4V to 12V supplies over a temperature range of −40°C to +125°C. They will operate well in ±5V or +5V to +12V power-supply systems. Parameters that vary significantly with operating voltage or temperature are shown in the Typical Characteristics. b) Dual− Supply Configuration Enable Digital Logic +5V OPA726 VOUT DGND − 5V ENABLE/SHUTDOWN OPA725 series op amps require approximately 4.3mA quiescent current. The enable/shutdown feature of the OPA726 allows the op amp to be shut off to reduce this current to approximately 6µA. The enable/shutdown input is referenced to the Enable Reference Pin, DGND (see Pin Configurations). This pin can be connected to logic ground in dual-supply op amp configurations to avoid level-shifting the enable logic signal, as shown in Figure 1. The Enable Reference Pin voltage, VDGND, must not exceed (V+) − 2V. It may be set as low as V−. The amplifier is enabled when the Enable Pin voltage is greater than VDGND + 2V. The amplifier is disabled (shutdown) if the Enable Pin voltage is less than VDGND + 0.8V. The Enable Pin is connected to internal pull-up circuitry and will enable the device if left unconnected. Figure 1. Enable Reference Pin Connection for Single- and Dual-Supply Configurations INPUT OVER-VOLTAGE PROTECTION Device inputs are protected by ESD diodes that will conduct if the input voltages exceed the power supplies by more than approximately 300mV. Momentary voltages greater than 300mV beyond the power supply can be tolerated if the current is limited to 10mA. This is easily accomplished with an input resistor in series with the op amp, as shown in Figure 2. The OPA725 series features no phase inversion when the inputs extend beyond supplies, if the input is current limited. COMMON-MODE VOLTAGE RANGE The input common-mode voltage range of the OPA725 and OPA726 series extends from V− to (V+) − 2V. Common-mode rejection is excellent throughout the input voltage range from V− to (V+) − 3V. CMRR decreases somewhat as the common-mode voltage extends to (V+) − 2V, but remains very good and is tested throughout this range. See the Electrical Characteristics table for details. VIN V+ IOVERLOAD 10mA max R OPA725 VOUT V− Figure 2. Input Current Protection for Voltages Exceeding the Supply Voltage 11 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 RAIL-TO-RAIL OUTPUT A class AB output stage with common-source transistors is used to achieve rail-to-rail output. This output stage is capable of driving heavy loads connected to any point between V+ and V−. For light resistive loads ( > 100kΩ ), the output voltage can swing to 150mV (175mV for dual) from the supply rail, while still maintaining excellent linearity (AOL > 110dB). With 1kΩ (2kΩ for dual) resistive loads, the output is specified to swing to within 250mV from the supply rails with excellent linearity (see the Typical Characteristics curve Output Voltage Swing vs Output Current). +5V 75Ω VIN ± 2.5V OPA725 AIN ADS8342 16− ADC Bit Common +5V 330pF − 5V −5V Figure 4. OPA725 Driving an ADC CAPACITIVE LOAD AND STABILITY Capacitive load drive is dependent upon gain and the overshoot requirements of the application. Increasing the gain enhances the ability of the amplifier to drive greater capacitive loads (see the Typical Characteristics curve Small-Signal Overshoot vs Capacitive Load). One method of improving capacitive load drive in the unity-gain configuration is to insert a 10Ω to 20Ω resistor inside the feedback loop, as shown in Figure 3. This reduces ringing with large capacitive loads while maintaining DC accuracy. TRANSIMPEDANCE AMPLIFIER Wide bandwidth, low input bias current, and low input voltage and current noise make the OPA725 an ideal wideband photodiode transimpedance amplifier. Lowvoltage noise is important because photodiode capacitance causes the effective noise gain of the circuit to increase at high frequency. The key elements to a transimpedance design, as shown in Figure 5, are the expected diode capacitance (CD), which should include the parasitic input common-mode and differential-mode input capacitance (4pF + 5pF for the OPA725); the desired transimpedance gain (RF); and the GBW for the OPA725 (20MHz). With these three variables set, the feedback capacitor value (CF) can be set to control the frequency response. CF includes the stray capacitance of RF, which is 0.2pF for a typical surface-mount resistor. V+ RS 20Ω OPA725 VOUT CL RL VIN CF(1) < 1pF Figure 3. Series Resistor in Unity-Gain Buffer Configuration Improves Capacitive Load Drive DRIVING FAST 16-BIT ADCs The OPA725 series is optimized for driving fast 16-bit ADCs such as the ADS8342. The OPA725 op amps buffer the converter input capacitance and resulting charge injection, while providing signal gain. Figure 4 shows the OPA725 in a single-ended method of interfacing to the ADS8342 16-bit, 250kSPS, 4-channel ADC with an input range of ±2.5V. The OPA725 has demonstrated excellent settling time to the 16-bit level within the 600ns acquisition time of the ADS8342. The RC filter, shown in Figure 4, has been carefully tuned for best noise and settling performance. It may need to be adjusted for different op amp configurations. Please refer to the ADS8342 data sheet (available for download at www.ti.com) for additional information on this product. 12 RF 10MΩ +5V λ CD OPA725 VOUT − 5V NOTE: (1) CF is optional to prevent gain peaking. It includes the stray capacitance of RF. Figure 5. Dual-Supply Transimpedance Amplifier OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 To achieve a maximally-flat, 2nd-order Butterworth frequency response, the feedback pole should be set to: 1 + 2pR FCF Bandwidth is calculated by: GBW 4pR FC D For additional information, refer to Application Bulletin SBOA055, Compensate Transimpedance Amplifiers Intuitively, available for download at www.ti.com. (1) OPTIMIZING THE TRANSIMPEDANCE CIRCUIT To achieve the best performance, components should be selected according to the following guidelines: 1. For lowest noise, select RF to create the total required gain. Using a lower value for RF and adding gain after the transimpedance amplifier generally produces poorer noise performance. The noise produced by RF increases with the square-root of RF, whereas the signal increases linearly. Therefore, signal-to-noise ratio is improved when all the required gain is placed in the transimpedance stage. Minimize photodiode capacitance and stray capacitance at the summing junction (inverting input). This capacitance causes the voltage noise of the op amp to be amplified (increasing amplification at high frequency). Using a low-noise voltage source to reverse-bias a photodiode can significantly reduce its capacitance. Smaller photodiodes have lower capacitance. Use optics to concentrate light on a small photodiode. Noise increases with increased bandwidth. Limit the circuit bandwidth to only that required. Use a capacitor across the RF to limit bandwidth, even if not required for stability. Circuit board leakage can degrade the performance of an otherwise well-designed amplifier. Clean the circuit board carefully. A circuit board guard trace that encircles the summing junction and is driven at the same voltage can help control leakage. f *3dB + GBW Hz 2pRFC D (2) For even higher transimpedance bandwidth, the high-speed CMOS OPA354 (100MHz GBW), OPA300 (180 MHz GBW), OPA355 (200MHz GBW), or OPA656, OPA657 (400MHz GBW) may be used. For single-supply applications, the +IN input can be biased with a positive dc voltage to allow the output to reach true zero when the photodiode is not exposed to any light, and respond without the added delay that results from coming out of the negative rail. (Refer to Figure 6.) This bias voltage also appears across the photodiode, providing a reverse bias for faster operation. CF(1) < 1pF 2. RF 10MΩ 3. V+ λ OPA725 4. VOUT +VBias NOTE: (1) CF is optional to prevent gain peaking. It includes the stray capacitance of RF. For additional information, refer to the Application Bulletins Noise Analysis of FET Transimpedance Amplifiers (SBOA060), and Noise Analysis for High-Speed Op Amps (SBOA066), available for download at the TI web site. Figure 6. Single-Supply Transimpedance Amplifier 13 OPA725, OPA2725 OPA726, OPA2726 www.ti.com SBOS278B − SEPTEMBER 2003 − REVISED JANUARY 2004 C1 1nF R3 2.07kΩ C3 2.2nF R1 1.93kΩ R2 15.9kΩ C2 330pF 1/2 OPA2725 R4 22.3kΩ C4 100pF 1/2 OPA2725 VOUT DC Gain = 1 Cutoff Frequency = 50kHz NOTE: FilterPro is a low-pass filter design program available for download at no cost from TI’s web site (www.ti.com). The program can be used to determine component values for other cutoff frequencies or filter types. Figure 7. Four-Pole Butterworth Sallen-Key Low-Pass Filter 14 PACKAGE OPTION ADDENDUM www.ti.com 4-Mar-2005 PACKAGING INFORMATION Orderable Device OPA2725AID OPA2725AIDGKR OPA2725AIDGKT OPA2725AIDR OPA2726AIDGSR OPA2726AIDGST OPA725AID OPA725AIDBVR OPA725AIDBVT OPA725AIDR OPA726AID OPA726AIDGKR OPA726AIDGKT OPA726AIDR (1) Status (1) ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE ACTIVE Package Type SOIC MSOP MSOP SOIC MSOP MSOP SOIC SOT-23 SOT-23 SOIC SOIC MSOP MSOP SOIC Package Drawing D DGK DGK D DGS DGS D DBV DBV D D DGK DGK D Pins Package Eco Plan (2) Qty 8 8 8 8 10 10 8 5 5 8 8 8 8 8 100 2500 250 2500 2500 250 100 3000 250 2500 100 2500 250 2500 None None None None None None None None None None None None None None Lead/Ball Finish CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU MSL Peak Temp (3) Level-3-240C-168 HR Level-1-240C-UNLIM Level-1-240C-UNLIM Level-3-240C-168 HR Level-1-240C-UNLIM Level-1-240C-UNLIM Level-3-240C-168 HR Level-1-240C-UNLIM Level-1-240C-UNLIM Level-3-240C-168 HR Level-3-240C-168 HR Level-2-240C-1 YEAR Level-2-240C-1 YEAR Level-3-240C-168 HR The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. None: Not yet available Lead (Pb-Free). Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens, including bromine (Br) or antimony (Sb) above 0.1% of total product weight. (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Amplifiers Data Converters DSP Interface Logic Power Mgmt Microcontrollers amplifier.ti.com dataconverter.ti.com dsp.ti.com interface.ti.com logic.ti.com power.ti.com microcontroller.ti.com Applications Audio Automotive Broadband Digital Control Military Optical Networking Security Telephony Video & Imaging Wireless Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright  2005, Texas Instruments Incorporated www.ti.com/audio www.ti.com/automotive www.ti.com/broadband www.ti.com/digitalcontrol www.ti.com/military www.ti.com/opticalnetwork www.ti.com/security www.ti.com/telephony www.ti.com/video www.ti.com/wireless