electronic circuits for optical systems : transimpedance amplifier (tia)
DESCRIPTION
2011-1 Special Topics in Optical Communications. Electronic Circuits for Optical Systems : Transimpedance Amplifier (TIA). Jin-Sung Youn ( [email protected] ) High-Speed Circuits & Systems Laboratory. 2011-1 Special Topics in Optical Communications. Contents. - PowerPoint PPT PresentationTRANSCRIPT
High-Speed Circuits & Systems Laboratory
Electronic Circuits for Optical Systems: Transimpedance Amplifier (TIA)
Jin-Sung Youn([email protected])
High-Speed Circuits & Systems Laboratory
2011-1 Special Topics in Optical Communications
High-Speed Circuits & Systems Laboratory
Contents
2
2011-1 Special Topics in Optical Communications
Electrical interconnects vs. optical interconnects
Electronic circuits for optical interconnects
- Receiver basics
- Transimpedance amplifier (TIA)
TIA design considerations
Advanced (wideband) techniques
Recent research topics
Conclusion
High-Speed Circuits & Systems Laboratory
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Electrical Interconnects2011-1 Special Topics in Optical Communications
Transmitter - Serializer: slow parallel data fast serial data - Phase-Locked Loop (PLL): generate reference clock - Pre-emphasis: compensate high-frequency loss
Receiver - Equalizer: compensate high-frequency loss - Limiting amplifier: amplify signal up to digital level - Clock and Data Recovery (CDR): recover synchronous clock and data - De-serializer: fast serial data slow parallel data
High-Speed Circuits & Systems Laboratory
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Optical Interconnects2011-1 Special Topics in Optical Communications
Direct modulation
- Driving circuits
- VCSEL
External modulation
- Laser
- Modulator
- Driving circuits
Photodetector
Current-voltage (I-V) conversion
component / circuits
High-Speed Circuits & Systems Laboratory
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Requirements for The First Block2011-1 Special Topics in Optical Communications
(Voltage / Power) Gain
(Channel) Bandwidth
Noise figure
RF Receiver Front-End Optical Receiver Front-End
(Transimpedance) Gain
(Broadband) Bandwidth
(Input) Noise current
High-Speed Circuits & Systems Laboratory
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Receiver Basics2011-1 Special Topics in Optical Communications
(Transimpedance) Gain
(Broadband) Bandwidth
(Input) Noise current
DGain R
12 D pd
BWR C
2, 2n in
D pd
kTIR C
► Resistor performs a current-to-voltage conversion.
Trade-off between gain, speed and noise !!
High-Speed Circuits & Systems Laboratory
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Integrated Total Noise2011-1 Special Topics in Optical Communications
Output Noise Spectrum of Circuit
Circuit bandwidth ↑ Integrated total noise ↑
High-Speed Circuits & Systems Laboratory
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Bandwidth vs. Noise2011-1 Special Topics in Optical Communications
BW = 1.4 fB
No ISI High noise
BW = 0.35 fB
High ISI Low noise
BW = 0.7 fB
No ISI Medium Noise
* ISI: Inter-Symbol Interference** fB: data rate
High-Speed Circuits & Systems Laboratory
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Bandwidth vs. Noise2011-1 Special Topics in Optical Communications
Inter-Symbol Interference (ISI) vs. Noise
Optimum bandwidth depends on data rates !!
High-Speed Circuits & Systems Laboratory
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Gain vs. Noise2011-1 Special Topics in Optical Communications
Signal-to-Noise Ratio (SNR)
pp
rms
[A ] [A ]
SignalSNR
Noise
Noise Ringing
GainBandwidth
Noise
High-Speed Circuits & Systems Laboratory
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Receiver Basics - Example2011-1 Special Topics in Optical Communications
High bandwidth
(fp = 15.9 GHz)
Low sensitivity
(Vo,pp = 9 mVpp)
High noise
Small bandwidth
(fp = 0.8 GHz)
High sensitivity
(Vo,pp = 1.8 Vpp)
Low noise
Low impedance High impedance** p-i-n photodetector ** (N.Feng et al., Optics Express, 2010)
1kΩ
(1) R = 0.9 A/W (TM polarization)
IIN = 1.8 mApp @ 0 dBm
(ideal extinction ratio)
(2) Cpd = 200 fF
RC time constant
High-Speed Circuits & Systems Laboratory
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Transimpedance Amplifier (TIA)2011-1 Special Topics in Optical Communications
(Shunt-Shunt) Feedback Amplifier
- Low input impedance & High transimpedance !!
(Transimpedance) Gain
(Broadband) Bandwidth
(Input) Noise current
A
1 FAGain R
A
12 F pd
ABWR C
2,2
, 2
4 n An in
F F
VkTIR R
11in FR R
A
Rin
High-Speed Circuits & Systems Laboratory
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Comparison2011-1 Special Topics in Optical Communications
But, RF ↑ Rin ↑
High-Speed Circuits & Systems Laboratory
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Advanced Techniques [1]2011-1 Special Topics in Optical Communications
Shunt Peaking
• Inductor implementation :(a) Spiral inductor(b) Active inductor
(a) Large power consumption & chip area (b) PVT variation
High-Speed Circuits & Systems Laboratory
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Advanced Techniques [2]2011-1 Special Topics in Optical Communications
Input (current) Buffer StageCommon-gate TIA (CG-TIA) Regulated-cascode TIA (RGC-TIA)
Rin
1
1in
m
Rg
Rin
1
11in
m mB B
Rg g R
Low input impedance a) higher input noise current b) Relatively low transimpedance gain G = RD // (RF/(A+1))
High-Speed Circuits & Systems Laboratory
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Advanced Techniques [3]2011-1 Special Topics in Optical Communications
Current-mode Transimpedance Amplifier (CM-TIA)
1
1in
m
Rg
Rin
Low input impedance a) Higher input noise current b) Low transimpedance gain @ low supply voltage G = Rout,M6 // Rout,M5
High-Speed Circuits & Systems Laboratory
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Receiver Front-End Integration2011-1 Special Topics in Optical Communications
Photodetector and electronic circuits should be integrated on a single chip for optical interconnect applications.
Responsivity Transimpedance gain [to meet limiting amplifier input sensitivity] Pole frequency - Transit effect - RC time constant TIA Input impedance [to avoid RC time effect] EQ gain [to compensate limited bandwidth] Noise Low input-referred circuit noise [to achieve high SNR at TIA input node]
Photodetector
High-Speed Circuits & Systems Laboratory
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Recent Research Topics2011-1 Special Topics in Optical Communications
“Receiver-less approach”
• Electronic circuit
- Low input MOSFET capacitance
- Low input sensitivity
• Photodetector
- High responsivity
- Low junction capacitance (~ fF)
Avalanche photodetector
(> p-i-n photodetector)
Power consumption of optical system should be minimized to take over a substantial fraction of interconnect applications.
Requirements
Buffer (inverter) chain
High-Speed Circuits & Systems Laboratory
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Receiver-Less Approach: Example2011-1 Special Topics in Optical Communications
** Avalanche photodetector ** (S.Assefa et al., Nature, 2010)
(1) R = 0.15 A/W
IIN = 0.3 mApp @ 0 dBm
(ideal extinction ratio)
(2) Cpd = 10 fF
RC time constant
High bandwidth (fp = 15.9 GHz)
High sensitivity (Vo,pp = 300 mVpp)
Low noise
(= 1kΩ)
High-Speed Circuits & Systems Laboratory
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Conclusion2011-1 Special Topics in Optical Communications
Receiver System for Optical Interconnects
Current-Voltage Conversion
Resistor termination
Transimpedance amplifier (TIA)
TIA design considerations & methods
Advanced (Wideband) techniques
Shunt-peaking
Common-gate & regulated cascode
Recent research topics Receiver-less approach !!
High-Speed Circuits & Systems Laboratory
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2011-1 Special Topics in Optical Communications
Thank you for listening !!
Jin-Sung Youn([email protected])
High-Speed Circuits & Systems Laboratory