® OPT211 MONOLITHIC PHOTODIODE AND AMPLIFIER FEATURES DESCRIPTION ● WIDE BANDWIDTH, HIGH RESPONSIVITY: The OPT211 is a monolithic photodiode with on-chip FET-input transpedance amplifier, that provides wide bandwidth at very high gains. Uncommitted input and feedback nodes allow a variety of feedback options for maximum versatility. Trade-offs in responsivity (gain), bandwidth and SNR can easily be made. BANDWIDTH 50kHz *150kHz 5kHz *13kHz *with bootstrap buffer ● PHOTODIODE SIZE: 0.090 x 0.090 inch (2.29 x 2.29mm) ● HIGH RESPONSIVITY: 0.45A/W (650nm) The monolithic combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs such as leakage current errors, noise pickup and gain peaking due to stray capacitance. The 0.09 x 0.09 inch photodiode is operated at zero bias for excellent linearity and low dark current. Direct access to the detector’s anode allows photodiode bootstrapping, which increases speed performance. ● LOW DARK ERRORS: 2mV max ● EXCELLENT SPECTRAL RESPONSE ● LOW QUIESCENT CURRENT: 400µA ● TRANSPARENT 8-PIN DIP APPLICATIONS The OPT211 operates over a wide supply range (±2.25V to ±18V) and supply current is only 400µA. It is packaged in a transparent plastic 8-pin DIP specified for the 0°C to 70°C temperature range. ● MEDICAL INSTRUMENTATION ● LABORATORY INSTRUMENTATION ● POSITION AND PROXIMITY SENSORS ● PHOTOGRAPHIC ANALYZERS ● BARCODE SCANNERS RF 2 OPT211 5 λ VOUT 0.5 Red Photodiode Responsivity (A/W) Ultraviolet Blue ● SMOKE DETECTORS SPECTRAL RESPONSIVITY Green Yellow RF 1MΩ 100MΩ Infrared Using External 1MΩ Resistor 0.4 0.3 0.2 0.1 0 7 8 1 100 3 200 300 400 500 600 700 800 900 1000 1100 Wavelength (nm) V+ V– 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/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1994 Burr-Brown Corporation PDS-1258B Printed in U.S.A. January, 1995 SPECIFICATIONS At TA = +25°C, VS = ±15V, λ = 650nm, external 1MΩ feedback resistor, circuit shown in Figure 1, unless otherwise noted. OPT211P PARAMETER CONDITIONS RESPONSIVITY Photodiode Current Unit-to-Unit Variation Voltage Output Nonlinearity Photodiode Area MIN 650nm 650nm λ = 650nm, RF = 1MΩ DARK ERRORS, RTO(1) Offset Voltage, Output vs Temperature vs Power Supply Voltage Noise, Dark (0.090 x 0.090 inches) (2.29 x 2.29mm) 0.45 ±5 0.45 0.01 0.008 5.2 VS = ±2.25V to ±18V Dark, fB = 0.1Hz to 100kHz ±0.5 ±10 10 1 FREQUENCY RESPONSE Bandwidth Rise Time, 10% to 90%, RF = 1MΩ Settling Time, FS to Dark 1% 0.1% 0.01% 100% Overload Recovery Time OUTPUT Voltage Output Anode Grounded(2) Anode Bootstrapped(3) Anode Grounded(2) Anode Bootstrapped(3) Anode Grounded(2) A/W % V/µW % of FS in2 mm2 ±2 100 mV µV/°C µV/V mVrms 10 25 30 44 100 240 µs µs µs µs µs µs (V+) – 1.25 (V+) – 2 (V+) – 1 (V+) – 1.5 250 ±18 V V pF mA ±2.25 ±15 ±400 VOUT = 0V TEMPERATURE RANGE Specification Operating Storage Thermal Resistance, θJA UNITS kHz kHz µs µs Operation(4) POWER SUPPLY Operating Voltage Range Quiescent Current MAX 50 150 5 2 FS to Dark (to 1%) VS = ±5V VS = ±2.25V RL = 10kΩ RL = 5kΩ Capacitive Load, Stable Short-Circuit Current TYP 0 0 –25 ±18 ±500 V µA +70 +70 +85 °C °C °C °C/W MAX UNITS 100 NOTES: (1) Referred to Output. Includes all error sources. (2) See Figure 1. (3) See Figure 3. (4) See Figure 2. PHOTODIODE SPECIFICATIONS At TA = +25°C, λ = 650nm, unless otherwise noted. Photodiode of OPT211 PARAMETER CONDITIONS Photodiode Area Current Responsivity Dark Current vs Temperature Capacitance MIN (0.090 x 0.090 inches) (2.29 x 2.29mm) λ = 650nm VD = 0V VD = 0V TYP 0.008 5.2 0.45 865 500 doubles every 10°C 600 in2 mm2 A/W µA/W/cm2 fA pF 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. ® OPT211 2 OP AMP SPECIFICATIONS TA = +25°C, VS = ±15V, RL = 10kΩ, unless otherwise noted. OPT211 Op Amp(1) PARAMETER INPUT Offset Voltage vs Temperature vs Power Supply Input Bias Current vs Temperature Input Impedance Differential Common-Mode Common-Mode Input Voltage Range Common-Mode Rejection CONDITIONS MIN TYP MAX UNITS ±0.5 ±5 10 ±1 doubles every 10°C mV µV/°C µV/V pA 1012 || 3 1012 || 3 ±14.4 106 Ω || pF Ω || pF V dB 30 25 15 0.8 nV/√Hz nV/√Hz nV/√Hz fA/√Hz OPEN-LOOP GAIN Open-Loop Voltage Gain 120 dB FREQUENCY RESPONSE Gain-Bandwidth Product(2) Slew Rate Settling Time 0.1% 0.01% 16 6 4 5 MHz V/µs µs µs (V+) – 1.25 (V+) – 2 (V+) – 1 (V+) – 1.5 ±18 V V mA ±2.25 ±15 ±400 NOISE Voltage Noise Density Current Noise Density OUTPUT Voltage Output VS = ±2.25V to ±18V Linear Operation f = 10Hz f = 100Hz f = 1kHz f = 1kHz RL = 10kΩ RL = 5kΩ Short-Circuit Current POWER SUPPLY Operating Voltage Range Quiescent Current IO = 0mA ±18 ±500 V µA NOTES: (1) Op amp specifications provided for information and comparison only. (2) Stable in gains ≥ 20V/V. ® 3 OPT211 ELECTROSTATIC DISCHARGE SENSITIVITY PIN CONFIGURATIONS Top View DIP V+ 1 –In 2 8 Common 7 PD Anode 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. (1) V– 3 6 NC NC 4 5 VOUT 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. NOTE: (1) Photodiode location. ABSOLUTE MAXIMUM RATINGS Supply Voltage ................................................................................... ±18V Input Voltage Range ............................................................................ ±VS Output Short-Circuit (to ground) ............................................... Continuous Operating Temperature ..................................................... –25°C to +85°C Storage Temperature ........................................................ –25°C to +85°C Junction Temperature ...................................................................... +85°C Lead Temperature (soldering, 10s) ................................................ +300°C (Vapor-Phase Soldering Not Recommended) MOISTURE SENSITIVITY AND SOLDERING Clear plastic does not contain the structural-enhancing fillers used in black plastic molding compound. As a result, clear plastic is more sensitive to environmental stress than black plastic. This can cause difficulties if devices have been stored in high humidity prior to soldering. The rapid heating during soldering can stress wire bonds and cause failures. Prior to soldering, it is recommended that plastic devices be baked-out at +85°C for 24 hours. PACKAGE INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) OPT211P 8-Pin DIP 006-1 The fire-retardant fillers used in black plastic are not compatible with clear molding compound. The OPT211 plastic packages cannot meet flammability test, UL-94. NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ® OPT211 4 TYPICAL PERFORMANCE CURVES At TA = +25°C, VS = ±15V, λ = 650nm, external 1MΩ feedback resistor, circuit shown in Figure 1, unless otherwise noted. NORMALIZED SPECTRAL RESPONSIVITY RESPONSE vs INCIDENT ANGLE 1.0 1.0 θX (0.48A/W) 0.8 0.8 650nm (0.45A/W) Relative Response Normalized Current or Voltage Output 1.0 0.6 0.4 0.6 0.6 θX 0.4 0.2 0.4 0.2 0 ±80 0 100 200 300 400 500 600 700 800 900 1000 1100 ±20 0 ±40 Wavelength (nm) ±60 Incident Angle (°) TRANSIMPEDANCE vs FREQUENCY VOLTAGE RESPONSIVITY vs RADIANT POWER 100M 10 10M Output Voltage (V) Dotted Line: Bandwidth with Bootstrap Buffer— See Text. RF = 100MΩ Transimpedance (V/A) θY Plastic DIP Package 0.2 0 RF = 10MΩ, CF = 1pF 1M RF = 1MΩ, CF = 3pF Ω 0M 1 RF = 0.1 10 Ω M RF = 10 RF = Ω 1M λ = 650nm 0.01 0.001 100k 1k 10k 100k 1M 10-3 10-2 Frequency (Hz) 10-1 102 QUIESCENT CURRENT vs TEMPERATURE VOLTAGE RESPONSIVITY vs IRRADIANCE 0.6 0.5 RF = Quiescent Current (mA) Ω M 00 1 1 Ω 0.1 RF = M 10 Ω RF 0.01 = 1M λ = 650nm VS = ±15V 0.4 0.3 VS = ±2.25V 0.2 0.1 0.001 10-4 101 10 Radiant Power (µW) 10 Output Voltage (V) 0.8 θY 0 10-3 10-2 10-1 10 101 –75 Irradiance (W/m2) –50 –25 0 25 50 75 100 125 Temperature (°C) ® 5 OPT211 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, λ = 650nm, external 1MΩ feedback resistor, circuit shown in Figure 1, unless otherwise noted. NOISE EFFECTIVE POWER vs MEASUREMENT BANDWIDTH OUTPUT NOISE VOLTAGE vs MEASUREMENT BANDWIDTH 10–2 10–8 Total Noise 0.1 Hz to Indicated BW 1MΩ Noise Effective Power (W) Noise Voltage (Vrms) 10–3 10–4 RF = 100MΩ 10–5 10–6 RF = 1MΩ RF = 10MΩ 10–7 1 10 100 1k OPT211 Anode Grounded OPT211 with Anode Bootstrap Drive 10k 100k λ = 650nm 10–9 10MΩ Total Noise 0.1 Hz to Indicated BW 10–10 100MΩ 10–11 10–12 OPT211 Anode Grounded OPT211 with Anode Bootstrap Drive 10–13 1M Frequency (Hz) 10–14 1 10 100 1k 10k Frequency (Hz) STEP RESPONSE RF = 1MΩ, Bootstrap Buffer STEP RESPONSE RF = 1MΩ, Anode Grounded ® OPT211 6 100k 1M APPLICATIONS INFORMATION Figure 1 shows the basic connections required to operate the OPT211. Applications with high impedance power supplies may require decoupling capacitors located close to the device pins as shown in Figure 1. stray capacitance to a few tenths of a picofarad. With experimentation, circuit board traces can be used to produce the necessary stray capacitance for proper compensation and widest possible bandwidth. The circuit in Figure 1 can drive capacitive loads up to 250pF. To drive load capacitance up to 1nF, connect R1 and the feedback components as shown in Figure 2. CF RF ≥ 330kΩ DARK ERRORS Dark error specifications include all error sources and are tested with the circuit shown in Figure 1 using RF=1MΩ. The dominate dark error source is the input offset voltage of the internal op amp. The combination of photodiode dark current and op amp input bias current is approximately 1.5pA at 25°C. Even with very large feedback resistors, this contributes virtually no offset error. Dark current and input bias current increase with temperature, doubling (approximately) for each 10°C increase. At 70°C, dark current is approximately 35pA. This would produce 3.5mV offset with a 100MΩ feedback resistor. 2 OPT211 ID 5 λ 7 8 1 VOUT 3 0.1µF 0.1µF V+ V– +15V –15V RF (Ω) CF (pF) Bandwidth (kHz) 330k 1M 10M 100M 5.6 3 1(1) 0.3(1) 86 50 16 5 Circuit board leakage currents can increase dark error. Use clean assembly procedures to avoid contamination, particularly around the sensitive inverting input node (pin 2). Errors due to leakage current from the V+ supply (pin 1) can be eliminated by encircling the trace connecting to pin 2 with a guard trace connected to ground. NOTE: (1) Feedback resistor has approximately 1pF stray capacitance. CF <1pF requires series-connected feedback resistors. See text. IMPROVING BANDWIDTH Bandwidth of the OPT211 can be increased with the feedback buffer circuits shown in Figure 3. Driving the anode of the photodiode (pin 7) in this manner reduces the effect of the photodiode’s capacitance on signal bandwidth. This “bootstrap drive” circuit boosts bandwidth by approximately 3x. Bandwidth achieved with various RF values is shown in Figure 2. When using a bootstrap buffer, RF must be greater or equal to 1MΩ for stable operation. FIGURE 1. Basic Circuit Connections. Output is zero volts with no light and increases with increasing illumination. Photodiode current is proportional to the radiant power (watts) falling in the photodiode. At 650nm wavelength (visible red) the photodiode responsivity is approximately 0.45A/W. Responsivity at other wavelengths is shown in the typical performance curve “Responsivity vs Wavelength.” RF The OPT211’s output voltage is the product of the photodiode current and feedback resistor, (IDRF). The feedback resistor must be greater than 330kΩ for proper stability. A feedback capacitor, CF, must be connected as shown. Recommended values are shown in Figure 1. Capacitor values for other feedback resistances can be interpolated. CF 2 OPT211 λ The OPT211 provides excellent performance with very high feedback resistor values. To achieve maximum bandwidth with RF ≥ 10MΩ, good circuit layout is required. With careful circuit board layout and a 10MΩ feedback resistor, stray capacitance will provide approximately the correct parallel capacitance for stable operation and widest bandwidth. For larger feedback resistor values, two resistors connected in series and laid-out end-to-end will reduce the R1 175Ω 5 VOUT CL≤1nF 7 8 1 3 0.1µF 0.1µF V+ V– FIGURE 2. Increasing C-Load Drive. ® 7 OPT211 AC COUPLING Bootstrap Buffer +15V R1 7.5kΩ Some applications are concerned only with sensing variation in light intensity. Simple capacitive coupling at the OPT211’s output may be adequate. With large feedback resistors or bright ambient light, however, the OPT211’s output may saturate. The circuit in Figure 4 can reject very bright ambient light, yet provide high AC gain for best signal-tonoise ratio. The output voltage is integrated and fed back to the inverting input through R3. This drives the average (dc) voltage at the output to zero. Application Bulletin AB-061 provides more details on this technique. CF Q1 2N5116 S RF ≥ 1MΩ D –15V 2 OPT211 5 λ 7 8 (a) VOUT C1 = C2 R1 = R2 1 3 +15V –15V f–3dB = C2 0.1µF RF R3(2πR2C2) 2 6 =16Hz OPA177 +15V Q1 2N6427 From Pin 2 From Pin 2 3 R1 1MΩ R3 1MΩ OPA131 R2 1MΩ C1 0.1µF RF = 10MΩ 2 To Pin 7 R1 6.8kΩ OPT211 To Pin 7 (c) (b) –15V 5 λ RF (Ω) 330k 1M 10M 100M CF (pF) Bandwidth (kHz) 7 Not Recommended 1(1) 150 <0.2(1) 42 (1) <0.2 13 1 V+ 3 V– See Application Bulletin AB-061 for details. FIGURE 4. Rejecting Ambient Light. NOTE: (1) Most resistors have approximately 1pF stray capacitance. CF<1pF requires series-connected feedback resistors. See text. This circuit also corrects output offset produced by input bias current of a buffer used to extend bandwidth. A Darlington transistor can be used for a bandwidth-enhancing bootstrap buffer in this circuit without creating offset error. FIGURE 3. Increasing Bandwidth with Bootstrap Buffer. Gate or base current of the buffer transistor flows through the feedback resistor, increasing the dark offset voltage. If dark errors are important, use a FET transistor with picoamp gate current. A P-channel FET is used to assure that the anode is at ground potential or slightly negative. NOISE PERFORMANCE Noise performance of the OPT211 is shown in typical curves for various feedback resistor values. This curve specifies the total noise measured from 0.1Hz to the indicated bandwidth. High frequency noise is reduced with the bootstrap transistor buffer circuits shown in Figure 1. This effect is shown on the typical curve. If dark errors are not critical, an NPN Darlington transistor can be used for a buffer as shown in Figure 3b. A FET-input op amp connected as a buffer can be used as shown in Figure 3c, but its noise may degrade circuit performance slightly. Bandwidth of the buffer should be 4MHz, minimum. Output noise of the OPT211 extends beyond the signal bandwidth, especially for high feedback resistor values. Signal-to-noise ratio can be improved by filtering the OPT211’s output to a bandwidth equal to the signal bandwidth—see Figure 5. ® OPT211 8 VOUT 8 Best signal-to-noise ratio is achieved by using the highest practical feedback resistor. This comes with the trade-off of decreased bandwidth. photodiode area allows easy positioning of narrowly focused light sources. The photodiode area is easily visible as it appears very dark compared to the surrounding active circuitry. The noise performance of a photodetector is sometimes characterized by its noise effective power (NEP). This is the radiant power which would produce an output signal equal to the output noise level. NEP has the units of radiant power (W). A NEP curve is provided. The incident angle of the light source also affects the apparent sensitivity in uniform irradiance. For small incident angles, the loss in sensitivity is simply due to the smaller effective light gathering area of the photodiode (proportional to the cosine of the angle). At a greater incident angle, light is diffracted and scattered by the side of the package. These effects are shown in the typical performance curve “Responsivity vs Incident Angle.” LIGHT SOURCE POSITIONING The OPT211 is 100% tested with a light source that uniformly illuminates the full area of the integrated circuit, including the op amp. Although all IC amplifiers are light-sensitive to some degree, the OPT211 op amp circuitry is designed to minimize this effect. Sensitive junctions are shielded with metal, and differential stages are cross-coupled. Furthermore, the photodiode area is very large relative to the op amp input circuitry making these effects negligible. LINEARITY PERFORMANCE The photodiode inside the OPT211 is designed to be operated in the photoconductive mode (VDIODE = 0V) for very linear operation with radiant power throughout a wide range. Nonlinearity remains below approximately 0.05% up to 100µA photodiode current. If your light source is focused to a small area, be sure that it is properly aimed to fall on the photodiode. If a narrowly focused light source were to miss the photodiode area and fall only on the op amp circuitry, the OPT211 would not perform properly. The large (0.090 inch x 0.090 inch) This very linear performance at high radiant power assumes that the full photodiode area is uniformly illuminated. If the light source is focused to a small area of the photodiode, nonlinearity will occur at lower radiant power. Sallen-Key Low Pass Filter Designed Using Burr-Brown’s Application Bulletin No. AB-034 RF = 10MΩ 2.2nF 2 OPT211 2 5 λ 7 8 1 V+ 3 2.94kΩ 21kΩ Sallen-Key 2-Pole Butterworth f–3dB = 20kHz 3 OPA131 6 VO 470pF V– FIGURE 5. Low Pass Filter for Improved Signal-to-Noise Ratio. ® 9 OPT211