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AD8015: 155 Mbps Transimpedance Amplifier

AD8015: 155 Mbps Transimpedance Amplifier
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AD8015: 155 Mbps Transimpedance Amplifier - 1

FUNCTIONAL BLOCK DIAGRAM 10kW 5 6 7 8 4 3 2 1 AD8015 50W +1 NC IIN NC VBYP –VS –OUTPUT +OUTPUT +VS G = 3 G = 30 NC = NO CONNECT 50W +1 – + +VS 1.7V 25.0E+3 20.0E+3 000.E+0 10.0E+6 100.0E+6 1.0E+9 15.0E+3 10.0E+3 5.0E+3 FREQUENCY – Hz X-RESISTANCE – W DIFFERENTIAL SINGLE-ENDED Figure 1. Differential/Single-Ended Transimpedance vs. Frequency 5.0 4.5 4.0 3.5 3.0 2.5 2.0 000.0E+0 20.0E+6 40.0E+6 60.0E+6 80.0E+6 100.0E+6 FREQUENCY – Hz EQUIVALENT INPUT CURRENT NOISE – pAÖHz 3.0pF 2.0pF 1.5pF 1.0pF 0.5pF Figure 2. Noise vs. Frequency (SO-8 Package with REV. A Added Capacitance) Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. a Wideband/Differential Output Transimpedance Amplifier AD8015 FEATURES Low Cost, Wide Bandwidth, Low Noise Bandwidth: 240 MHz Pulse Width Modulation: 500 ps Rise Time/Fall Time: 1.5 ns Input Current Noise: 3.0 pA/ÖHz @ 100 MHz Total Input RMS Noise: 26.5 nA to 100 MHz Wide Dynamic Range Optical Sensitivity: –36 dBm @ 155.52 Mbps Peak Input Current: 6350 mA Differential Outputs Low Power: 5 V @ 25 mA Wide Operating Temperature Range: –408C to +858C APPLICATIONS Fiber Optic Receivers: SONET/SDH, FDDI, Fibre Channel Stable Operation with High Capacitance Detectors Low Noise Preamplifiers Single-Ended to Differential Conversion I-to-V Converters PRODUCT DESCRIPTION The AD8015 is a wide bandwidth, single supply transimpedance amplifier optimized for use in a fiber optic receiver circuit. It is a complete, single chip solution for converting photodiode current into a differential voltage output. The 240 MHz bandwidth enables AD8015 application in FDDI receivers and SONET/SDH receivers with data rates up to 155 Mbps. This high bandwidth supports data rates beyond 300 Mbps. The differential outputs drive ECL directly, or can drive a comparator/ fiber optic post amplifier. In addition to fiber optic applications, this low cost, silicon alternative to GaAs-based transimpedance amplifiers is ideal for systems requiring a wide dynamic range preamplifier or singleended to differential conversion. The IC can be used with a standard ECL power supply (–5.2 V) or a PECL (+5 V) power supply; the common mode at the output is ECL compatible. The AD8015 is available in die form, or in an 8-pin SOIC package. © Analog Devices, Inc., 1996 One Technology Way, P.O. Box 9106, Norwood, 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703

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AD8015: 155 Mbps Transimpedance Amplifier - 2

AD8015–SPECIFICATIONS –2– REV. A (SO Package @ TA = +258C and VS = +5 V, unless otherwise noted) AD8015AR Parameter Conditions Min Typ Max Units DYNAMIC PERFORMANCE Bandwidth 3 dB 180 240 MHz Pulse Width Modulation 10 mA to 200 mA Peak 500 ps Rise and Fall Time 10% to 90% 1.5 ns Settling Time1 to 3%, 0.5 V Diff Output Step 3 ns INPUT Linear Input Current Range ±2.5%, Nonlinearity ±25 ±30 mA Max Input Current Range Saturation ±200 ±350 mA Optical Sensitivity 155 Mbps, Avg Power –36 dBm Input Stray Capacitance Die, by Design 0.2 pF SOIC, by Design 0.4 pF Input Bias Voltage +VS to IIN and VBYP...

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AD8015: 155 Mbps Transimpedance Amplifier - 3

AD8015 REV. A –3– . V1 +VS CLOCK LPF: RECOVERY 3dB@ 0.7 x F LPF: 3dB@ 0.7 x F QUANTIZER R > 40W C1 >100pF 4.5V < VS < 11V CLK DATA R R C1 10kW 5 6 7 8 4 3 2 1 AD8015 50W +1 G = 3 G = 30 50W +1 – + +VS 1.7V 1.7V +VS Figure 3. Fiber Optic Receiver Application: Photodiode Referred to Positive Supply PHOTODIODE REFERRED TO NEGATIVE SUPPLY Figure 4 shows the AD8015 used in a circuit where the photodiode is referred to the negative supply. This results in a larger back bias voltage than when referring the photodiode to the positive supply. The larger back bias voltage on the photodiode decreases...

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AD8015: 155 Mbps Transimpedance Amplifier - 4

–4– REV. A AD8015 SONET OC-3 SENSITIVITY ANALYSIS OC-3 Minimum Bandwidth = 0.7 ´ 155 MHz » 110 MHz Total Current Noise = (p/2) ´ 26.5 nA = 42 nA (assuming single pole response) To maintain a BER < 1 ´ 10–10 (1 error per 10 billion bits): Minimum current level needs to be > 13 ´ Total Current Noise = 541 nA (peak) Assume a typical photodiode current/power conversion ratio = 0.85 A/W Sensitivity (minimum power level) = 541/0.85 nW = 637 nW (peak) = –32.0 dBm (peak) = –35.0 dBm (average) The SONET OC-3 specification allows for a minimum power level of –31 dBm peak, or –34 dBm average. Using...

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AD8015: 155 Mbps Transimpedance Amplifier - 6

–6– REV. A AD8015 100 50 1 10 100 1000 FREQUENCY – MHz 0 5V, +25°C PIN 7 PIN 6 IMPEDANCE – W Figure 12. Output Impedance vs. Frequency 100 –100 0 20 0 10 TIME – ns VOLTAGE – mV Figure 13. Small Signal Pulse Response 2 0 –12 10.0E+6 100.0E+6 1.0E+9 –2 –4 –6 –8 –10 0pF 1pF 3pF 5pF 8pF FREQUENCY – Hz GAIN – dB Figure 14. Differential Gain vs. Input Capacitance APPLICATION 155 Mbps Fiber Optic Receiver The AD8015 and AD807 can be used together for a complete 155 Mbps Fiber Optic Receiver (Transimpedance Amplifier, Post Amplifier with Signal Detect Output, and Clock Recovery and Data Retiming)...

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AD8015: 155 Mbps Transimpedance Amplifier - 8

–8– REV. A AD8015 PRINTED IN U.S.A. C1973–6–1/96 AC COUPLED PHOTODIODE APPLICATION FOR IMPROVED DYNAMIC RANGE AC coupling the photodiode current input to the AD8015 (Figure 17) extends fiber optic receiver overload by 3 dB while sacrificing only 1 dB of sensitivity (increasing receiver dynamic range by 2 dB). This application results in typical overload of –4 dBm, and typical sensitivity of –35 dBm. AC coupling the input also results in improved pulse width modulation performance. Careful attention to minimize parasitic capacitance at the AD8015 input (from the photodetector input), RAC and...

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