(R) OPT101 FPO 70 MONOLITHIC PHOTODIODE AND SINGLE-SUPPLY TRANSIMPEDANCE AMPLIFIER FEATURES DESCRIPTION The OPT101 is a monolithic photodiode with on-chip transimpedance amplifier. Output voltage increases linearly with light intensity. The amplifier is designed for single or dual power supply operation, making it ideal for battery operated equipment. The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs such as leakage current errors, noise pick-up and gain peaking due to stray capacitance. The 0.09 x 0.09 inch photodiode is operated in the photoconductive mode for excellent linearity and low dark current. The OPT101 operates from +2.7V to +36V supplies and quiescent current is only 120A. It is available in clear plastic 8-pin DIP, 5-pin SIP and J-formed DIP for surface mounting. Red plastic versions are also available with optical filter properties, providing selective response to wavelengths greater than 580nm. Temperature range is 0C to 70C. SINGLE SUPPLY: +2.7 to +36V PHOTODIODE SIZE: 0.090 x 0.090 inch INTERNAL 1M FEEDBACK RESISTOR HIGH RESPONSIVITY: 0.45A/W (650nm) BANDWIDTH: 14kHz at RF = 1M LOW QUIESCENT CURRENT: 120A AVAILABLE IN 8-PIN DIP, 5-PIN SIP, AND 8-LEAD SURFACE MOUNT PACKAGES CLEAR OR RED PLASTIC VERSIONS APPLICATIONS MEDICAL INSTRUMENTATION LABORATORY INSTRUMENTATION POSITION AND PROXIMITY SENSORS PHOTOGRAPHIC ANALYZERS BARCODE SCANNERS SMOKE DETECTORS CURRENCY CHANGERS SPECTRAL RESPONSIVITY 0.6 (2) 1 3pF 1M 4 (4) 8pF 5 (5) 7.5mV Voltage Output (V/W) 2 0.7 Infrared 0.6 0.5 0.5 Using Internal 1M Resistor 0.4 0.4 0.3 0.3 Red "-R" Package Versions 0.2 0.1 0.1 0 VB 200 OPT101 (1) 8 (SIP) 0.2 300 400 500 600 700 800 Wavelength (nm) 900 Photodiode Responsivity (A/W) Ultraviolet V+ Red (Pin available on DIP only.) Blue 0.7 Green Yellow 0 1000 1100 (3) 3 DIP 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 * Cable: BBRCORP * Telex: 066-6491 * FAX: (520) 889-1510 * Immediate Product Info: (800) 548-6132 (c) 1994 Burr-Brown Corporation PDS-1257B Printed in U.S.A. August, 1995 SPECIFICATIONS TA = +25C, VS = +2.7V to +36V, = 650nm, internal 1M feedback resistor, and RL = 10k unless otherwise noted. OPT101P, W PARAMETER CONDITIONS RESPONSIVITY Photodiode Current Voltage Output vs Temperature Unit to Unit Variation Nonlinearity(1) Photodiode Area DARK ERRORS, RTO(2) Offset Voltage, Output vs Temperature vs Power Supply Voltage Noise, Dark, fB = 0.1Hz to 20kHz MIN 650nm 650nm 650nm FS Output = 24V (0.090 x 0.090in) (2.29 x 2.29mm) +5 VS = +2.7V to +36V VS = +15V, VPIN3 = -15V POWER SUPPLY Operating Voltage Range Quiescent Current +7.5 2.5 10 300 1 0.5 0.5 50 VOUT = 10Vp-p VOUT = 10V Step VOUT = 10V Step 100%, Return to Linear Operation OUTPUT Voltage Output, High Capacitive Load, Stable Operation Short-Circuit Current MAX 0.45 0.45 100 5 0.01 0.008 5.2 TRANSIMPEDANCE GAIN Resistor Tolerance, P W vs Temperature FREQUENCY RESPONSE Bandwidth Rise Fall Time, 10% to 90% Settling Time, 0.05% 0.1% 1% Overload Recovery TYP (VS) - 1.3 VS = 36V +10 100 2 mV V/C V/V Vrms M % % ppm/C kHz s s s s s (VS) - 1.15 10 15 V nF mA 120 220 TEMPERATURE RANGE Specification Operating Storage Thermal Resistance, JA A/W V/W ppm/C % % of FS in2 mm2 14 28 160 80 70 50 +2.7 Dark, VPIN3 = 0V RL = , VOUT = 10V UNITS 0 0 -25 +36 240 V A A +70 +70 +85 C C C C/W MAX UNITS 100 NOTES: (1) Deviation in percent of full scale from best-fit straight line. (2) Referred to Output. Includes all error sources. PHOTODIODE SPECIFICATIONS TA = +25C, VS = +2.7V to +36V unless otherwise noted. Photodiode of OPT101P PARAMETER CONDITIONS Photodiode Area Current Responsivity Dark Current vs Temperature Capacitance MIN (0.090 x 0.090in) (2.29 x 2.29mm) 650nm 650nm VDIODE = 7.5mV TYP 0.008 5.2 0.45 865 2.5 doubles every 7C 1200 in2 mm2 A/W A/W/cm2 pA 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. (R) OPT101 2 OP AMP SPECIFICATIONS TA = +25C, VS = +2.7V to +36V, = 650nm, internal 1M feedback resistor, and RL = 10k unless otherwise noted. OPT101 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 2.5 10 165 1 mV V/C V/V pA pA/C 400 || 5 250 || 35 0 to [(VS) - 1] 90 M || pF G || pF V dB OPEN-LOOP GAIN Open-loop Voltage Gain 90 dB FREQUENCY RESPONSE Gain-Bandwidth Product(2) Slew Rate Settling Time 1% 0.1% 0.05% 2 1 5.8 7.7 8.0 MHz V/s s s s (VS) - 1.15 15 V mA OUTPUT Voltage Output, High Short-Circuit Current POWER SUPPLY Operating Voltage Range Quiescent Current (-) Input (-) Input Linear Operation (VS) - 1.3 VS = +36V +2.7 Dark, VPIN3 = 0V RL , VOUT = 10V 120 220 +36 240 V A A NOTES: (1) Op amp specifications provided for information and comparison only. (2) Stable gains 10V/V. MOISTURE SENSITIVITY AND SOLDERING ELECTROSTATIC DISCHARGE SENSITIVITY 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 +85C for 24 hours. 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. The fire-retardant fillers used in black plastic are not compatible with clear molding compound. The OPT101 plastic packages cannot meet flammability test, UL-94. (R) 3 OPT101 DICE INFORMATION Photodiode Area 0.090 x 0.090 inch 2.29 x 2.29mm 5 8 Feedback Resistor Amplifier PAD FUNCTION 1 2 3 4 5 8 VS -In -V 1M Feedback Output Common MECHANICAL INFORMATION 4 2 1 3 Die Size Die Thickness Min. Pad Size MILS (0.001") MILLIMETERS 150 x 120 18 4x4 3.81 x 3.05 0.51 0.1 x 0.1 Backing None NOTE: Pad numbers correspond to pin numbers on DIP package. PIN CONFIGURATIONS ABSOLUTE MAXIMUM RATINGS Top View Supply Voltage (VS to "Common" or pin 3) ................................ 0 to +36V Output Short-Circuit (to ground) ............................................... Continuous Operating Temperature ..................................................... -25C to +85C Storage Temperature ........................................................ -25C to +85C Junction Temperature ...................................................................... +85C Lead Temperature (soldering, 10s) ................................................ +300C (Vapor-Phase Soldering Not Recommended) DIP VS 1 8 Common -In 2 7 NC -V 3 6 NC 1M Feedback 4 5 Output (1) PACKAGE INFORMATION NOTE: (1) Photodiode location. MODEL Top View SIP Common 1 VS 2 -V 3 1M Feedback 4 Output 5 OPT101P OPT101P-R OPT101P-J OPT101P-R-J OPT101W OPT101W-R (1) PACKAGE PACKAGE DRAWING NUMBER(1) Clear Red Clear Red Clear Red 8-Pin Plastic DIP 8-Pin Plastic DIP 8-Lead Surface Mount(2) 8-Lead Surface Mount(2) 5-Pin Plastic SIP 5-Pin Plastic SIP 006-1 006-1 006-4 006-4 321 321 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. (2) 8-pin DIP with J-formed leads for surface mounting. (R) OPT101 COLOR 4 TYPICAL PERFORMANCE CURVES TA = +25C, VS = +2.7V to +36V, = 650nm, internal 1M feedback resistor, and RL = 10k unless otherwise noted. Red Blue Ultraviolet 0.9 VOLTAGE RESPONSIVITY vs RADIANT POWER 10 Green Yellow Infrared 70C 0.8 25C 0.7 0.6 Output Voltage (V) Normalized Current or Voltage Output NORMALIZED SPECTRAL RESPONSIVITY 1.0 650nm (0.45A/W) 0.5 0.4 Red "-R" Package Versions 0.3 M 1 RF = 0.1 10 RF = 1M 0k RF = 10 k 0.01 RF 0.2 = = 650nm 50 0.1 0 200 0.001 300 400 500 600 700 800 Wavelength (nm) 900 1000 1100 0.01 0.1 1 10 100 1k Radiant Power (W) VOLTAGE RESPONSIVITY vs IRRADIANCE VOLTAGE RESPONSIVITY vs FREQUENCY 10 10 1 M RF = 10 0.1 RF = 1M RF 0.01 0k = 10 k RF = 50 0.01 0.1 1 Irradiance RF = 1M 0.1 10 0.001 100 100 1.0 8 0.8 7.8 X Y Y 0.6 Output Voltage (mV) Relative Response SIP Package 0.6 X 0.4 Plastic DIP Package Y 0.4 0.2 0 20 40 10k 100k 60 DARK VOUT vs TEMPERATURE 7.6 7.4 7.2 0.2 0 1k Frequency (Hz) RESPONSE vs INCIDENT ANGLE X RF = 50k, CEXT = 56pF (W/m2) 1.0 0.8 RF = 100k, CEXT = 33pF 0.01 = 650nm 0.001 0.001 1 Responsivity (V/W) Output Voltage (V) RF = 10M 7 0 80 0 Incident Angle () 10 20 30 40 Temperature (C) 50 60 70 (R) 5 OPT101 TYPICAL PERFORMANCE CURVES (CONT) TA = +25C, VS = +2.7V to +36V, = 650nm, internal 1M feedback resistor, and RL = 10k unless otherwise noted. QUIESCENT CURRENT vs TEMPERATURE 300 QUIESCENT CURRENT vs (VOUT - VPIN3) 300 250 VS = 15V, VOUT - VPIN3 = 15V Quiescent Current (A) Quiescent Current (A) 250 225 200 VS = 5V, VOUT - VPIN3 = 5V 175 150 VS = +15V, VOUT - VPIN3 = 0V 125 100 200 VS = 2.7V 150 100 50 75 VS = +5V, VOUT - VPIN3 = 0V 50 0 0 10 20 30 40 Temperature (C) 50 60 70 0 5 18 160 16 140 14 120 12 10 8 6 15 20 25 VOUT - VPIN3 (V) IFEEDBACK (IBIAS-IDARK) 30 35 40 3pF 1M 100 8pF 80 IBIAS 60 40 IDARK 20 4 0 2 -20 VB OPT101 8 (1) -40 0 0 5 10 15 20 VS (V) 25 30 35 40 0 OUTPUT NOISE VOLTAGE vs MEASUREMENT BANDWIDTH, VS = +15, VOUT - VPIN3 = 15V RF = 10M 10-7 RF = 1MINTERNAL Noise Effective Power (W) Noise Voltage (Vrms) 10 (IBIAS-IDARK) vs TEMPERATURE 180 IBIAS-IDARK (pA) Short Circuit Current (mA) SHORT CIRCUIT CURRENT vs VS 20 1000 VS = 15V VS = 36V 275 RF = 100k || 33pF 100 10 RF = 50k || 56pF 1 10 20 30 40 Temperature (C) 50 60 70 NOISE EFFECTIVE POWER vs MEASUREMENT BANDWIDTH, VS = +15, VOUT - VPIN3 = 0 10-8 RF = 100k || 33pF 10-9 RF = 50k || 56pF RF = 1M INTERNAL 10-10 RF = 10M 10-11 10-12 0.1 10 100 1k 10k Frequency (Hz) 100k 10 1M (R) OPT101 6 100 1k 10k Bandwidth (Hz) 100k 1M TYPICAL PERFORMANCE CURVES (CONT) TA = +25C, VS = +2.7V to +36V, = 650nm, internal 1M feedback resistor, and RL = 10k unless otherwise noted. SMALL SIGNAL RESPONSE LARGE SIGNAL RESPONSE SMALL SIGNAL RESPONSE (CLOAD = 10,000 pF) (Pin 3 = 0V) SMALL SIGNAL RESPONSE (CLOAD = 10,000 pF) (Pin 3 = -15V) (R) 7 OPT101 APPLICATIONS INFORMATION source to sink currents up to approximately 100A. The benefits of this current sink are shown in the typical performance curves "Small Signal Response (CLOAD = 10,000pF)" which compare operation with pin 3 grounded and connected to -15V. Figure 1 shows the basic connections required to operate the OPT101. Applications with high-impedance power supplies may require decoupling capacitors located close to the device pins as shown. Output is 7.5mV dc with no light and increases with increasing illumination. Due to the architecture of this output stage current sink, there is a slight increase in operating current when there is a voltage between pin 3 and the output. Depending on the magnitude of this voltage, the quiescent current will increase by approximately 100A as shown in the typical performance curve "Quiescent Current vs (VOUT - VPIN3)". Photodiode current, ID, is proportional to the radiant power, or flux, (in watts) falling on the photodiode. At a wavelength of 650nm (visible red) the photodiode Responsivity, RI, is approximately 0.45A/W. Responsivity at other wavelengths is shown in the typical performance curve "Responsivity vs Wavelength." VS VS = +2.7 to +36V 2 (Pin available on DIP only.) 2 0.01 to 0.1F (Pin available on DIP only.) 1 (2) 3pF 1 (2) 3pF 1M 0.01 to 0.1F 1M 4 (4) 4 (4) 8pF 8pF 5 (5) 5 (5) VB OPT101 8 (1) Dark output 7.5mV Positive going output with increased light VB OPT101 8 (1) 3 (3) 3 (3) 0.01 to 0.1F Common -V = -1V to (VS - 36V) Common FIGURE 1. Basic Circuit Connections. FIGURE 2. Bipolar Power Supply Circuit Connections. The typical performance curve "Output Voltage vs Radiant Power" shows the response throughout a wide range of radiant power. The response curve "Output Voltage vs Irradiance" is based on the photodiode area of 5.2mm2. NOISE PERFORMANCE Noise performance of the OPT101 is determined by the op amp characteristics, feedback components and photodiode capacitance. The typical performance curve "Output Noise Voltage vs Measurement Bandwidth" shows how the noise varies with RF and measured bandwidth (0.1Hz to the indicated frequency), when the output voltage minus the voltage on pin 3 is greater than approximately 50mV. Below this level, the output stage is powered down, and the effective bandwidth is decreased. This reduces the noise to approximately 1/3 the nominal noise value of 300Vrms, or 100Vrms. This enables a low level signal to be resolved. The OPT101's voltage output is the product of the photodiode current times the feedback resistor, (IDRF), plus a pedestal voltage, VB, of approximately 7.5mV introduced for single supply operation. The internal feedback resistor is laser trimmed to 1M. Using this resistor, the output voltage responsivity, RV, is approximately 0.45V/W at 650nm wavelength. Figure 1 shows the basic circuit connections for the OPT101 operating with a single power supply and using the internal 1M feedback resistor for a response of 0.45V/W at 650nm. Pin 3 is connected to common in this configuration. Noise can be reduced by filtering the output with a cutoff frequency equal to the signal bandwidth. This will improve signal-to-noise ratio. Also, output noise increases in proportion to the square root of the feedback resistance, while responsivity increases linearly with feedback resistance. Best signal-to-noise ratio is achieved with large feedback resistance. This comes with the trade-off of decreased bandwidth. CAPACITIVE LOADING The OPT101 is capable of driving load capacitances of 10nF without instability. However, dynamic performance with capacitive loads can be improved by applying a negative bias voltage to Pin 3 (shown in Figure 2). This negative power supply voltage allows the output to go negative in response to the reactive effect of a capacitive load. An internal JFET connected between pin 5 (output) and pin 3 allows the output to sink current. This current sink capability can also be useful when driving the capacitive inputs of some analog-to-digital converters which require the signal The noise performance of the photodetector is sometimes characterized by Noise Effective Power (NEP). This is the radiant power that would produce an output signal equal to the noise level. NEP has the units of radiant power (watts), or Watts/Hz to convey spectral information about the noise. The typical performance curve "Noise Effective Power" vs Measurement Bandwidth" illustrates the NEP for the OPT101. (R) OPT101 8 DARK ERRORS The dark errors in the specification table include all sources. The dominant source of dark output voltage is the "pedestal" voltage applied to the non-inverting input of the op amp. This voltage is introduced to provide linear operation in the absence of light falling on the photodiode. Photodiode dark current is approximately 2.5pA and contributes virtually no offset error at room temperature. The bias current of the op amp's summing junction (- input) is approximately 165pA. The dark current will be subtracted from the amplifier's bias current, and this residual current will flow through the feedback resistor creating an offset. The effects of temperature on this difference current can be seen in the typical performance curve "(IBIAS - IDARK) vs Temperature." The dark output voltage can be trimmed to zero with the optional circuit shown in Figure 3. A low impedance offset driver (op amp) should be used to drive pin 8 (DIP) because this node has signal-dependent currents. This capacitor eliminates gain peaking and prevents instability. The value of CEXT can be determined from the table in Figure 4. Values of RF, other than shown in the table, can be interpolated. VS 3pF 1M 8pF 2 VB OPT101 3pF 4 (4) 8pF 5 (5) VB OPT101 8 (1) Common 3 (3) (a)-Series REXT (for SIP package). 1 (2) 1M CEXT 5 Pin Numbers: DIP (SIP) VS 4 (4) REXT (5) 8 (1) (Pin available on DIP only.) Pin Numbers: DIP (SIP) 1 (2) 2 REXT (M) CEXT (pF) DC Gain (x106V/A) Bandwidth (kHz) 1 2 5 10 50 50 25 10 5 -- 2 3 6 11 51 8 6 2.5 1.3 0.33 CEXT VO Adjust R1 for VO = 0V with no light. REXT VS 3 (3) 1 (2) 2 -V 3pF 4 1M +15V OPA177 8pF R1 500k 5 1/2 REF200 100A -15V -15V VB OPT101 FIGURE 3. Dark Error (Offset) Adjustment Circuit. 8 CHANGING RESPONSIVITY An external resistor, REXT, can be connected to set a different voltage responsivity. To increase the responsivity, this resistor can be placed in series with the internal 1M (Figure 4a), or with the DIP package, the external resistor can replace the internal resistor by not connecting pin 4 (Figure 4b). The second configuration also allows the circuit gain to be reduced below 106V/A by using external resistors of less than 1M. 3 (b)-External Feedback (for DIP package). REXT (M) CEXT (pF) DC Gain (x106V/A) Bandwidth (kHz) 0.05(1) 0.1(1) 1 2 5 10 50 56 33 -- -- -- -- -- 0.05 0.1 1 2 5 10 50 58 44 23 9.4 3.6 1.8 0.34 Note: (1) May require 1k in series with pin 5 when driving large capacitances. Figure 4 includes tables showing the responsivity and bandwidth. For values of RF less than 1M, an external capacitor, CEXT should be connected in parallel with RF. FIGURE 4. Changing Responsivity with External Resistor. (R) 9 OPT101 LIGHT SOURCE POSITIONING The OPT101 is tested with a light source that uniformly illuminates the full area of the integrated circuit, including the op amp. Although IC amplifiers are light-sensitive to some degree, the OPT101 op amp circuitry is designed to minimize this effect. Sensitive junctions are shielded with metal, and the photodiode area is very large relative to the op amp input circuitry. approximately 14kHz. The R and C values are 1M and 11pF respectively. By using external resistors, with less than 3pF parasitic capacitance, the frequency response can be improved. An external 1M resistor used in the configuration shown in Figure 4b will create a 23kHz bandwidth with the same 106V/A dc transimpedance gain. This yields a rise time of approximately 15s (10% to 90%). Dynamic response is not limited by op amp slew rate. This is demonstrated by the dynamic response oscilloscope photographs showing virtually identical large-signal and small-signal response. If your light source is focused to a small area, be sure that it is properly aimed to fall on the photodiode. A narrowly focused beam falling on only the photodiode will provide improved settling times compared to a source that uniformly illuminates the full area of the die. If a narrowly focused light source were to miss the photodiode area and fall only on the op amp circuitry, the OPT101 would not perform properly. The large 0.09" x 0.09" (2.29mm x 2.29mm) 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. Dynamic response will vary with feedback resistor value as shown in the typical performance curve "Responsivity vs Frequency." Rise time (10% to 90%) will vary according to the -3dB bandwidth produced by a given feedback resistor value: tr = 0.35 fC where: tr is the rise time (10% to 90%) fC is the -3dB bandwidth The incident angle of the light source also effects 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 package. These effects are shown in the typical performance curve "Responsivity vs Incident Angle." LINEARITY PERFORMANCE The photodiode is operated in the photoconductive mode so the current output of the photodiode is very linear with radiant power throughout a wide range. Nonlinearity remains below approximately 0.05% up to 100A photodiode current. The photodiode can produce output currents of 1mA or greater with high radiant power, but nonlinearity increases to several percent in this region. DYNAMIC RESPONSE Using the internal 1M resistor, the dynamic response of the photodiode/op amp combination can be modeled as a simple R * C circuit with a -3dB cutoff frequency of 2 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. 1 0.01 to 0.1F 3pF 4 1M +2.7 to +36V 8pF 5 VOUT VB OPT101 8 3 NOTE: Pin Numbers for DIP Package. FIGURE 5. Three-Wire Remote Light Measurement. (R) OPT101 10 +15V 1 2 3pF 4 1M 8pF +15V V01 Difference Output 2 7 1 5 6 RG VB 5 8 OPT101 3 8 50k RG 4 3 -15V +15V 1 2 VOUT = (V02 - V01) 1+ INA118 3pF +15V Log of Ratio Measurement (Absorbance) 4 1M 6 8pF 100k 100k 5 LOG100 VOUT = K log10 (V02/V01) 7 1 V02 14 9 VB 1nF 3 OPT101 8 3 -15V NOTE: OPT101 Pin Numbers for DIP Package. FIGURE 6. Differential Light Measurement. +15V 2 1 3pF 3.3nF 1M +15V +15V 10k 2 REF102 10V 7 2 OPA627 100k 3 6 6 270 5 LED 4 VB IN4148 4 4 8pF -15V 11k OPT101 0.03F 8 3 Glass Microscope Slide Approximately 92% light available for application. LED 8% OPT101 NOTE: OPT101 Pin Numbers for DIP Package. FIGURE 7. LED Output Regulation Circuit. (R) 11 OPT101