CMOS Optical Preamplifier Design Using Graphical Circuit Analysis

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3.3 A Low-Voltage Transimpedance Amplifier 68 Figure 3.23 Main charge pump for doubling the input bias voltage. Finally, the output switches and are driven by the third charge-pump, high- lighted in Figure 3.24. Compared to the central charge pump, the third charge-pump uses a slightly lower level-shift voltage so that the gate-source voltages of switches M 7 C 3 and are 0V when the switches are open and 1V when the switches are closed. Although the output switches could have been connected to the central pump, the additional charge pump provides an added degree of freedom for improv- ing the output resistance of the switch. For example, given a worse case threshold voltage of -0.8V, the gate-source voltage in excess of the threshold would be reduced to 0.05V. With the separate charge pump, this voltage is 0.2V, or four times greater. M 3 Φ 1VB M 8 V B- =0.7V C 5 Φ 1 M 5 M 1 V B =0.85V M 7 M 7 M 2 M 8 M 8 M 4 C 4 Φ 2VB V B- =0.7V M 6 Φ 2 C 6 0.85V 0.85V Figure 3.24 Charge pump for driving output switches. 1V 0.7V 1.70V 1.70V
3.3 A Low-Voltage Transimpedance Amplifier 69 The bias voltage doubler requires non-overlapping clock signals to clearly define the two phases of the circuit’s operation. A non-overlapping clock generator based on [Martin,1981] was incorporated into the doubler circuit and is shown in Figure 3.25. Figure 3.25 Non-overlapping clock generator. To illustrate the expanded range of the proposed bias voltage doubler over that of the basic charge pump cell shown in Figure 3.19, we ran two simulations of the two circuits at start up. For the basic charge pump, the supply voltage was equal to the desired bias voltage. A small output load capacitance of 0.5 pF was chosen to speed up the transient response. The first simulation used an input voltage of 0.85V and is shown in Figure 3.26. We see that both circuits come to within 20mV of the ideal level. The slight undershoot is a result of parasitic capacitance on the top plates of the level-shifting capacitors. This undershoot can be easily compensated for by increasing the input bias voltage. The response of the proposed doubler is faster due to the reduced switch resistance afforded by the dedicated charge pump driving the output switches. In the second simulation, the input bias voltage is reduced to 0.75V. As shown in Figure 3.27, only the proposed doubler circuit man- ages to reach the desired level in this case. With the basic charge pump, the 0.75V supply provides a reduced clock swing that is barely enough to initially turn on M 1 External clock switches and , and the switches quickly become ineffective as the threshold M 2 voltages of switches and increase due to the body effect. M 1 M 2 Φ 1 Φ 2
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CMOS Optical Preamplifier Design Us
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To achieve low-voltage operation, w
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Table of Contents CHAPTER 1 INTRODU
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CHAPTER 1 1.1 OVERVIEW Introduction
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Information Source Modulator Drive
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1.2 Thesis Outline 5 [Ohhata,1999].
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1.2 Thesis Outline 7 technique call
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1.2 Thesis Outline 9 Detector in St
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E e + - V bias 2.1 Photodetectors 1
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Diode Capacitance (pF) Diode capaci
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2.2 Optical Preamplifier Structures
Page 23 and 24: 2.3 Transimpedance Amplifier Design
Page 27 and 28: I dc 2.3 Transimpedance Amplifier D
Page 31 and 32: Source Figure 2.11 General structur
Page 33 and 34: A = = For = 1V , the solution is v
Page 35 and 36: The gain of the forward amplifier c
Page 37 and 38: Feedback Analysis Using Return Rati
Page 39 and 40: 2.4 Circuit Analysis Techniques 33
Page 41 and 42: 2.5 An Overview of Signal-Flow Grap
Page 43 and 44: 1 x1 x2 2.5 An Overview of Signal-F
Page 45 and 46: 2.6 SUMMARY REFERENCES • ∆ k =
Page 47 and 48: Symp. Circuits Systems, vol. 3, pp.
Page 49 and 50: CHAPTER 3 New Transimpedance Amplif
Page 51 and 52: 3.1 A Differential Transimpedance A
Page 57 and 58: 3.2 A Feedback Topology for Ambient
Page 59 and 60: 3.2 A Feedback Topology for Ambient
Page 61 and 62: Transimpedance (dBΩ) 90 80 60 40
Page 63 and 64: 3.3 A Low-Voltage Transimpedance Am
Page 73: C 3 Φ1VB M 3 V B- =0.7V M 7 Figure
Page 77 and 78: 3.4 SUMMARY 3.4 Summary 71 In this
Page 79 and 80: 3.4 Summary 73 Y. Nakagome et al.,
Page 81 and 82: 4.1 Introduction 75 back topology o
Page 83 and 84: 4.2 Circuit Analysis Using Driving-
Page 91 and 92: 4.3 DPI/SFG: Combining DPI Analysis
Page 93 and 94: 4.4 Determining Port Impedances 87
Page 95 and 96: v i R in v o R out 4.4 Determining
Page 97 and 98: id » ro and 1 ⁄ rid « Av ⁄ ro
Page 103 and 104: Z b r e g m 4.5 Analyzing Transisto
Page 105 and 106: 4.5 Analyzing Transistor Circuits 9
Page 107 and 108: Figure 4.25 SFG for the source foll
Page 115 and 116: 5.1 Analysis of the Low-Voltage Tra
Page 117 and 118: 5.1 Analysis of the Low-Voltage Tra
Page 119 and 120: 5.2 DEVELOPING AN ANALYTIC CIRCUIT
Page 121 and 122: Z in 5.2 Developing an Analytic Cir
Page 123 and 124: 5.2 Developing an Analytic Circuit
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I n1 : i in I n2 -I n1 i scin ( sCi
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5.2 Developing an Analytic Circuit
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I nRf : 5.2 Developing an Analytic
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DC transimpedance gain: Pole locati
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Frequency (MHz) 500 450 400 350 300
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Pole frequencies(MHz) 500 450 400 3
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Optimizing Sensitivity 5.2 Developi
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5.2 Developing an Analytic Circuit
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Transimpedance Volts dB (lin) Gain
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CHAPTER 6 Implementation and Experi
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6.1 A 1V Optical Receiver Front-End
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6.1.2 Experimental Results 6.1 A 1V
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Gain(dB) 0 −1 −2 −3 −4 −5
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Clock signal of voltage doubler Eye
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6.2 Variable-Gain Transimpedance Am
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6.2.2 Experimental Results 6.2 Vari
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6.3 Summary and State-of-the-Art Co
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Reference Outputs Technology Supply
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CHAPTER 7 Conclusions 7.1 SUMMARY A
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7.2 Future Work 165 The significanc
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7.2 Future Work 167 supply and subs
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v s i ti that part of the SFG for Q
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Thus, P1 ′ = b = 500Ω ∆1 ′
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itive representation of circuit dyn
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Bipolar Transistor i scb Z b v b b
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CMOS Optical Preamplifier Design Using Graphical Circuit Analysis

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