学校代码：10246 学号：073021253 狐旦大孥 硕士学位论文 (专业学位) 基准电压源和线性稳压器的设计 院 系：信息科学与工程学院 专 业： 集成电路工程 姓 名： 刘立明 指导教师： 唐长文副教授 完成日期： 2010年4月16日
学校代码： 10246 学 号： 073021253 硕 士 学 位 论 文 （专业学位） 基准电压源和线性稳压器的设计 院 系： 信息科学与工程学院 专 业： 集成电路工程 姓 名： 刘立明 指 导 教 师： 唐长文 副教授 完 成 日 期： 2010 年 4 月 16 日
目录 图目录 表目录… VI 摘要 …1 Abstract… …3 第一章概述… …5 1.1研究动机… 5 1.2研究内容及贡献… 5 1.3论文组织结构… 6 第二章带隙基准电压源电路设计 …7 2.1前言… …7 2.1.1主要性能指标 2.1.2基本结构及原理… P 2.2电路结构及性能分析 11 2.3误差分析… …14 2.4温度系数分析 …16 2.5噪声分析 …17 26电路实现… 20 2.7仿真结果 23 2.7.1直流特性… 24 2.7.2环路交流特性 26 2.7.3PSR特性… 29 2.7.4噪声… 31 2.7.5自启动… 32 2.7.6数字修正 34 28电路性能总结… 35 第三章电压一电流转换电路设计 37 3.1前言… 37 3.2电路结构及性能分析… 40 3.3电路实现 41 3.4仿真结果 42 3.5电路性能总结 43 第四章低压差线性稳压器设计 …45 4.1前言… 45
I 目 录 图目录 ·········································································································III 表目录 ······································································································· VII 摘 要 ··········································································································1 Abstract ······································································································3 第一章 概述 ·······························································································5 1.1 研究动机 ························································································5 1.2 研究内容及贡献··············································································5 1.3 论文组织结构 ·················································································6 第二章 带隙基准电压源电路设计 ·······························································7 2.1 前言································································································7 2.1.1 主要性能指标·······································································7 2.1.2 基本结构及原理···································································8 2.2 电路结构及性能分析·····································································11 2.3 误差分析 ······················································································14 2.4 温度系数分析 ···············································································16 2.5 噪声分析 ······················································································17 2.6 电路实现 ······················································································20 2.7 仿真结果 ······················································································23 2.7.1 直流特性············································································24 2.7.2 环路交流特性·····································································26 2.7.3 PSR 特性···········································································29 2.7.4 噪声···················································································31 2.7.5 自启动 ···············································································32 2.7.6 数字修正············································································34 2.8 电路性能总结 ···············································································35 第三章 电压—电流转换电路设计 ·····························································37 3.1 前言······························································································37 3.2 电路结构及性能分析·····································································40 3.3 电路实现 ······················································································41 3.4 仿真结果 ······················································································42 3.5 电路性能总结 ···············································································43 第四章 低压差线性稳压器设计·································································45 4.1 前言······························································································45
4.2电路结构及性能分析 48 4.3电路实现… 50 4.4仿真结果 51 4.4.1直流特性… 52 4.4.2环路交流特性 53 4.4.3PSRR特性… 58 4.4.4负载变化… 59 4.4.5噪声… 60 4.5电路性能总结 60 第五章总结与展望 63 5.1总结… 63 5.2展望 63 致谢… 65 参考文献… …67
II 4.2 电路结构及性能分析·····································································48 4.3 电路实现 ······················································································50 4.4 仿真结果 ······················································································51 4.4.1 直流特性············································································52 4.4.2 环路交流特性·····································································53 4.4.3 PSRR 特性········································································58 4.4.4 负载变化············································································59 4.4.5 噪声···················································································60 4.5 电路性能总结 ···············································································60 第五章 总结与展望···················································································63 5.1 总结······························································································63 5.2 展望······························································································63 致谢············································································································65 参考文献·····································································································67
图目录 图1-1系统结构… …6 图2-1带隙基准电压源电路拓扑结构…9 图2-2带隙基准电压源核心电路…。 10 图2-3典型带隙基准电压源电路的温度系数…10 图2-4带隙基准电压源电路原理图… 11 图2-5数字控制带隙基准电压源原理图…12 图2-6可控PNP晶体管组基本单元… 13 图2-7简单的差分放大器…13 图2-8引起带隙基准电压源电路误差的因素… …14 图2-9MOS管的变化对输出参考电压温度曲线的影响… …15 图2-10电阻的变化对输出参考电压温度曲线的影响… …15 图2-11双极型晶体管的变化对输出参考电压温度曲线的影响…16 图2-12温度曲线… …16 图2-3带隙基准电压源的等效噪声电路… …18 图2-14差分放大器的噪声源… 20 图2-15带隙基准电压源电路图… 21 图2-16误差放大器电路结构… 21 图2-17RC滤波器频率特性 22 图2-18RC低通滤波器对PSR的影响… 23 图2-19RC低通滤波器对噪声的影响… 23 图2-20电源变化与温度曲线的关系… 25 图2-21VoD为3.3V时工艺角与温度曲线的关系… 25 图2-22V0加为2.1V时工艺角与温度曲线的关系… … 26 图2-23电源变化与环路交流特性的关系… 27 图2-24电源变化与单位增益带宽的关系… 27 图2-25电源变化与相位裕度的关系… 28 图2-26VoD为2.1V时工艺角与环路交流特性的关系 28 图2-276加为3.3V时工艺角与环路交流特性的关系…29 图2-28电源变化与PSR的关系 30 图2-29bD为3.3V时工艺角与PSR的关系… 31 图2-30Voo为2.1V时工艺角与PSR的关系 31 图2-31电源变化与噪声的关系… 32 图2-32电源变化与启动时间的关系… 33
III 图目录 图 1-1 系统结构 ··························································································6 图 2-1 带隙基准电压源电路拓扑结构 ··························································9 图 2-2 带隙基准电压源核心电路 ·······························································10 图 2-3 典型带隙基准电压源电路的温度系数··············································10 图 2-4 带隙基准电压源电路原理图····························································11 图 2-5 数字控制带隙基准电压源原理图·····················································12 图 2-6 可控 PNP 晶体管组基本单元··························································13 图 2-7 简单的差分放大器··········································································13 图 2-8 引起带隙基准电压源电路误差的因素··············································14 图 2-9 MOS 管的变化对输出参考电压温度曲线的影响 ·····························15 图 2-10 电阻的变化对输出参考电压温度曲线的影响·································15 图 2-11 双极型晶体管的变化对输出参考电压温度曲线的影响···················16 图 2-12 温度曲线 ······················································································16 图 2-13 带隙基准电压源的等效噪声电路···················································18 图 2-14 差分放大器的噪声源·····································································20 图 2-15 带隙基准电压源电路图·································································21 图 2-16 误差放大器电路结构·····································································21 图 2-17 RC 滤波器频率特性······································································22 图 2-18 RC 低通滤波器对 PSR 的影响 ·····················································23 图 2-19 RC 低通滤波器对噪声的影响 ·······················································23 图 2-20 电源变化与温度曲线的关系··························································25 图 2-21 VDD为 3.3 V 时工艺角与温度曲线的关系······································25 图 2-22 VDD为 2.1 V 时工艺角与温度曲线的关系······································26 图 2-23 电源变化与环路交流特性的关系···················································27 图 2-24 电源变化与单位增益带宽的关系···················································27 图 2-25 电源变化与相位裕度的关系··························································28 图 2-26 VDD为 2.1 V 时工艺角与环路交流特性的关系·······························28 图 2-27 VDD为 3.3 V 时工艺角与环路交流特性的关系·······························29 图 2-28 电源变化与 PSR 的关系·······························································30 图 2-29 VDD为 3.3 V 时工艺角与 PSR 的关系···········································31 图 2-30 VDD为 2.1 V 时工艺角与 PSR 的关系···········································31 图 2-31 电源变化与噪声的关系·································································32 图 2-32 电源变化与启动时间的关系··························································33
图2-33Vbo为3.3V时工艺角与启动时间的关系…33 图2-34bD为2.1V时工艺角与启动时间的关系… …34 图2-35bD为2.1V时数字修正与温度曲线的关系…35 图2-36Voo为3.3V时数字修正与温度曲线的关系 …35 图3-1电压一电流转换电路拓扑图… 37 图3-2电流镜示意图… 38 图3-3由于Vs不同产生输出电流的误差… 39 图3-4共源共栅(cascade)电流镜…. …39 图3-5低压共源共栅电流镜… 40 图3-6电压一电流转换电路原理图… 41 图3-7电压一电流转换电路… 41 图3-8电源变化和工艺角偏差与输出电流的关系… 42 图4-1电源管理示意图… …45 图4-2恒压源及其连接示意图… 46 图4-3线性稳压器的典型输入一输出特性… 46 图4-4传统的线性稳压器… 47 图4-5传统的线性稳压器的波特图… 47 图4-6低压差线性稳压器… 47 图4-7低压差线性稳压器的波特图… 47 图4-8低压差线性稳压器结构示意图… 48 图4-9负载电流快速切换的等效电路… 49 图4-10快速瞬态响应的无片外电容的稳压器的原理图… 49 图4-11简单的电容积分器… 50 图4-12快速瞬态响应的稳压器等效电路图… 50 图4-13低压差线性稳压器电路图…。 51 图4-14低压差线性稳压器仿真电路图… 51 图4-15电源变化和负载电流与温度曲线的关系… 52 图4-16电源变化与输出电压的关系… 53 图4-1730mA范围内，负载电流变化与单位增益带宽的关系…54 图4-1830A范围内，负载电流变化与相位裕度的关系 55 图4-191mA范围内，负载电流变化与单位增益带宽的关系…55 图4-201A范围内，负载电流变化与相位裕度的关系 56 图4-21电源电压和负载与环路交流稳定性的关系…56 图4-22相位裕度… 57 图4-23单位增益带宽… 57 图4-24电源电压和负载与PSRR的关系… 58 V
IV 图 2-33 VDD为 3.3 V 时工艺角与启动时间的关系······································33 图 2-34 VDD为 2.1 V 时工艺角与启动时间的关系······································34 图 2-35 VDD为 2.1 V 时数字修正与温度曲线的关系 ··································35 图 2-36 VDD为 3.3 V 时数字修正与温度曲线的关系 ··································35 图 3-1 电压—电流转换电路拓扑图····························································37 图 3-2 电流镜示意图 ·················································································38 图 3-3 由于 VDS不同产生输出电流的误差·················································39 图 3-4 共源共栅(cascade)电流镜······························································39 图 3-5 低压共源共栅电流镜·······································································40 图 3-6 电压—电流转换电路原理图····························································41 图 3-7 电压—电流转换电路·······································································41 图 3-8 电源变化和工艺角偏差与输出电流的关系 ······································42 图 4-1 电源管理示意图··············································································45 图 4-2 恒压源及其连接示意图···································································46 图 4-3 线性稳压器的典型输入—输出特性·················································46 图 4-4 传统的线性稳压器··········································································47 图 4-5 传统的线性稳压器的波特图····························································47 图 4-6 低压差线性稳压器··········································································47 图 4-7 低压差线性稳压器的波特图····························································47 图 4-8 低压差线性稳压器结构示意图 ························································48 图 4-9 负载电流快速切换的等效电路 ························································49 图 4-10 快速瞬态响应的无片外电容的稳压器的原理图 ·····························49 图 4-11 简单的电容积分器 ········································································50 图 4-12 快速瞬态响应的稳压器等效电路图 ···············································50 图 4-13 低压差线性稳压器电路图 ·····························································51 图 4-14 低压差线性稳压器仿真电路图 ······················································51 图 4-15 电源变化和负载电流与温度曲线的关系········································52 图 4-16 电源变化与输出电压的关系··························································53 图 4-17 30 mA 范围内，负载电流变化与单位增益带宽的关系··················54 图 4-18 30 mA 范围内，负载电流变化与相位裕度的关系 ·························55 图 4-19 1 mA 范围内，负载电流变化与单位增益带宽的关系····················55 图 4-20 1 mA 范围内，负载电流变化与相位裕度的关系 ···························56 图 4-21 电源电压和负载与环路交流稳定性的关系 ····································56 图 4-22 相位裕度 ······················································································57 图 4-23 单位增益带宽 ···············································································57 图 4-24 电源电压和负载与 PSRR 的关系··················································58
图4-25负载电流跳变对输出电压的影响…59
V 图 4-25 负载电流跳变对输出电压的影响···················································59
表目录 表2-1电源变化与静态功耗的关系… …24 表2-2工艺角与静态功耗的关系…24 表2-3温度系数… 26 表2-4电源电压和工艺角与环路交流稳定性的关系…29 表2-5电源变化与PSR的关系… 30 表2-6电源电压和工艺角与噪声的关系…32 表2-7数字控制输出参考电压。 34 表2-8带隙基准电压源的性能…36 表4-1电源变化与静态功耗的关系… 52 表4-2工艺角与静态功耗的关系… … 52 表4-3电源电压和负载与环路交流稳定性的关系… 53 表4-4电源电压和工艺角与环路交流稳定性的关系… … 58 表4-5电源电压和负载与PSRR的关系… 59 表4-6输出电压的变化… 60 表4-7电源电压和负载与噪声的关系…60 表4-8电源电压和工艺角与噪声的关系… 60 表4-9低压差线性稳压器电路的性能… 61 VII
VII 表目录 表 2-1 电源变化与静态功耗的关系····························································24 表 2-2 工艺角与静态功耗的关系 ·······························································24 表 2-3 温度系数 ························································································26 表 2-4 电源电压和工艺角与环路交流稳定性的关系···································29 表 2-5 电源变化与 PSR 的关系·································································30 表 2-6 电源电压和工艺角与噪声的关系·····················································32 表 2-7 数字控制输出参考电压···································································34 表 2-8 带隙基准电压源的性能···································································36 表 4-1 电源变化与静态功耗的关系····························································52 表 4-2 工艺角与静态功耗的关系 ·······························································52 表 4-3 电源电压和负载与环路交流稳定性的关系 ······································53 表 4-4 电源电压和工艺角与环路交流稳定性的关系···································58 表 4-5 电源电压和负载与 PSRR 的关系····················································59 表 4-6 输出电压的变化··············································································60 表 4-7 电源电压和负载与噪声的关系 ························································60 表 4-8 电源电压和工艺角与噪声的关系·····················································60 表 4-9 低压差线性稳压器电路的性能 ························································61
摘要 近年来由于工艺水平不断提高，电路设计技术不断进步，集成电路行业发 展迅速，应用领域不断扩展。但同时，对电路的性能要求越来越苛刻。基准源 为其他电路模块提供稳定精确的电压/电流，其性能影响电路的整体性能。 本文设计的带隙基准电压源对电源电压、工艺和温度的变化不敏感，具有高 电源电压抑制和低噪声的特点。电路中使用数字控制的PNP晶体管阵列进行软修 正。该带隙基准电压源电路能为其他电路模块提供稳定精确的电压。从仿真结果 来看，其温度系数小于28.38ppm/℃，Voo为3.3V时直流的电源抑制比为88.9 dB,Vbp为2.1V时直流的电源抑制比为65dB。从100Hz到100kHz范围的积分 噪声为13Vms。 本文设计的电压一电流转换电路使用片外可调电阻，将带隙基准电压源产生 的输出参考电压转换成稳定的电流。在电源电压和工艺的变化下其输出电流的变 化小于0.5%。 最后本文设计了低压差线性稳压器，电路的补偿结构可以使输出电压快速瞬 态响应外界负载的变化。极端条件下，相位裕度为40deg,其他条件下相位裕度 大于88deg。Vop为3.3V时直流的电源抑制比为60dB,Voo为2.1V时直流的电 源抑制比为40dB。从100Hz到100kHz范围的积分噪声为24Vms。输出电压 瞬态响应的变化小于100mV。 本文选用中芯国际的0.18-m CMOS工艺库模型进行仿真。 关键词：带隙基准电压源、低压差线性稳压器、高电源电压抑制、低噪声、软 修正、快速瞬态响应 中图分类号：TN432
1 摘 要 近年来由于工艺水平不断提高，电路设计技术不断进步，集成电路行业发 展迅速，应用领域不断扩展。但同时，对电路的性能要求越来越苛刻。基准源 为其他电路模块提供稳定精确的电压/电流，其性能影响电路的整体性能。 本文设计的带隙基准电压源对电源电压、工艺和温度的变化不敏感，具有高 电源电压抑制和低噪声的特点。电路中使用数字控制的PNP晶体管阵列进行软修 正。该带隙基准电压源电路能为其他电路模块提供稳定精确的电压。从仿真结果 来看，其温度系数小于28.38 ppm/℃，VDD为3.3 V时直流的电源抑制比为88.9 dB，VDD为2.1 V时直流的电源抑制比为65 dB。从100 Hz到100 kHz范围的积分 噪声为13 μVrms。 本文设计的电压—电流转换电路使用片外可调电阻，将带隙基准电压源产生 的输出参考电压转换成稳定的电流。在电源电压和工艺的变化下其输出电流的变 化小于0.5 ‰。 最后本文设计了低压差线性稳压器，电路的补偿结构可以使输出电压快速瞬 态响应外界负载的变化。极端条件下，相位裕度为40 deg，其他条件下相位裕度 大于88 deg。VDD为3.3 V时直流的电源抑制比为60 dB，VDD为2.1 V时直流的电 源抑制比为40 dB。从100 Hz到100 kHz范围的积分噪声为24 μVrms。输出电压 瞬态响应的变化小于100 mV。 本文选用中芯国际的0.18-μm CMOS工艺库模型进行仿真。 关键词：带隙基准电压源、低压差线性稳压器、高电源电压抑制、低噪声、软 修正、快速瞬态响应 中图分类号：TN432
Abstract In recent years,as the technology of semiconductor has improved continuously,and the circuit design technology continues to progress,the IC industry has been growing quickly,the applications continue to be widely.But at the same,that require the circuits must have higher performances. In this work,the bandgap voltage reference is insensitive with the variations of power-supply,process,and temperature,with a high power supply rejection and low noise.There is a digital control circuit to modify the number of the PNP transistor arrays,as soft-trimming.The circuit produces a stable and accurate voltage to all other integrated circuits.The simulation results are given,the temperature coefficient is less than 28.38 ppm/C.When Vop is 3.3 V the Power-Supply Rejection is 88.9 dB at DC,it is 65 dB when VDD is 2.1 V.The integrated noise from 100 Hz to 100 kHz is 13 uVrms. In this work,there is an off-chip adjustable resistance for the voltage to current converter circuit.The circuit converts the output reference voltage from the bandgap voltage reference,to a stable current.As the power supply and process vary,the variation of the output current is less than 0.5%. Finally,there is a LDO(Low Dropout Regulator)voltage regulator,the compensation scheme provides a fast transient response for output voltage as the load change.Under the extreme condition,the phase margin is 40 deg. The other conditions,phase margin are more than 88 deg.The Power-Supply Rejection is 60 dB at DC when VDD is 3.3 V,it is 40 dB when VDD is 2.1 V.The integrated noise from 100 Hz to 100 kHz is 24 uVrms.The variation of the transient response of the output is less than 100 mV. This work bases on the SMIC 0.18-um CMOS process to simulate. Keywords:Bandgap Voltage Reference,LDO,High PSRR,Low Noise, Soft-trimming,Fast Transient Response Classification Code:TN432 3
3 Abstract In recent years, as the technology of semiconductor has improved continuously, and the circuit design technology continues to progress, the IC industry has been growing quickly, the applications continue to be widely. But at the same, that require the circuits must have higher performances. In this work, the bandgap voltage reference is insensitive with the variations of power-supply, process, and temperature, with a high power supply rejection and low noise. There is a digital control circuit to modify the number of the PNP transistor arrays, as soft-trimming. The circuit produces a stable and accurate voltage to all other integrated circuits. The simulation results are given, the temperature coefficient is less than 28.38 ppm/℃. When VDD is 3.3 V the Power-Supply Rejection is 88.9 dB at DC, it is 65 dB when VDD is 2.1 V. The integrated noise from 100 Hz to 100 kHz is 13 μVrms. In this work, there is an off-chip adjustable resistance for the voltage to current converter circuit. The circuit converts the output reference voltage from the bandgap voltage reference, to a stable current. As the power supply and process vary, the variation of the output current is less than 0.5 ‰. Finally, there is a LDO(Low Dropout Regulator) voltage regulator, the compensation scheme provides a fast transient response for output voltage as the load change. Under the extreme condition, the phase margin is 40 deg. The other conditions, phase margin are more than 88 deg. The Power-Supply Rejection is 60 dB at DC when VDD is 3.3 V, it is 40 dB when VDD is 2.1 V. The integrated noise from 100 Hz to 100 kHz is 24 μVrms. The variation of the transient response of the output is less than 100 mV. This work bases on the SMIC 0.18-μm CMOS process to simulate. Keywords: Bandgap Voltage Reference，LDO，High PSRR，Low Noise， Soft-trimming，Fast Transient Response Classification Code: TN432
第一章概述 第一章概述 1.1研究动机 基准源是集成电路的重要基本单元电路，包括基准电压源和基准电流源。其 性能的好坏对整体性能影响较大。基准源除用做电源外，还为其他电路模块提供 精确的参考电压/电流。例如，将基准电压源作为运算放大器的参考输入，模数 转换器(ADC)中用于比较的标准电压等[1]。 好的稳定性是对基准源的主要要求，即对外部条件（如工作温度和电源电压 等)变化不敏感。基准的噪声和偏差都会严重地影响电路中其他模块的精度和稳 定性。因此，系统的精确度在很大程度上由基准的精度决定。基准源的性能不好， 则系统性能很难达到设计要求。 基准电压源和基准电流源并不是孤立的，电压基准可以转换为电流基准，反 之亦然。本文中电流基准源由电压基准源电路的输出参考电压转换得到。系统内 部的模块一般为电流偏置，等同于镜像基准电流，所以电流基准源必须稳定精确。 片上系统(SOC)是集成电路设计的主要趋势之一[2]。减少片外器件，减少 引脚，包含更多的子模块，减少流片、封装和测试等费用，进而降低成本。使 用线性稳压器时，其输出端的负载电流和负载电容随外接负载变化而变化，这 些变化将影响线性稳压器的稳定性，其输出电压不稳定。传统的低压差线性稳 压器需接容值较大的片外电容，使其性能稳定，可以快速响应瞬态变化。但增 加引脚意味着增加费用。无片外电容的低压差线性稳压需要增加特殊结构，用 来完成快速瞬态响应。该结构越简单越好，所需元件减少，直流功耗小：只改 善瞬态特性，不影响低压差线性稳压的直流特性。 1.2研究内容及贡献 本文设计完成了带隙基准电压源电路、电压一电流转换电路和低压差线性 稳压器电路，各部分的相互关系如图1-1所示。 带隙基准电压源电路使用数字信号控制PNP双极型晶体管数目，调整输 出参考电压，进行修正，消除温度和工艺等产生的影响。选用合适的双极型晶 体管比值和电阻的比值，可以实现低噪声的输出电压。在输出端加RC低通滤 波器滤除高频噪声，高频性能得到改善。 电压一电流转换电路使用片外可调电阻，抵消工艺产生的偏差。输出电流 支路采用低电压共源共栅结构，该结构可以增加输出阻抗，输出的偏置电流更 准确。 低压差线性稳压器的设计中增加自动检测网络，在外界负载变化较大时， 5
第一章 概述 5 第一章 概述 1.1 研究动机 基准源是集成电路的重要基本单元电路，包括基准电压源和基准电流源。其 性能的好坏对整体性能影响较大。基准源除用做电源外，还为其他电路模块提供 精确的参考电压/电流。例如，将基准电压源作为运算放大器的参考输入，模数 转换器(ADC)中用于比较的标准电压等[1]。 好的稳定性是对基准源的主要要求，即对外部条件(如工作温度和电源电压 等)变化不敏感。基准的噪声和偏差都会严重地影响电路中其他模块的精度和稳 定性。因此，系统的精确度在很大程度上由基准的精度决定。基准源的性能不好， 则系统性能很难达到设计要求。 基准电压源和基准电流源并不是孤立的，电压基准可以转换为电流基准，反 之亦然。本文中电流基准源由电压基准源电路的输出参考电压转换得到。系统内 部的模块一般为电流偏置，等同于镜像基准电流，所以电流基准源必须稳定精确。 片上系统(SOC)是集成电路设计的主要趋势之一[2]。减少片外器件，减少 引脚，包含更多的子模块，减少流片、封装和测试等费用，进而降低成本。使 用线性稳压器时，其输出端的负载电流和负载电容随外接负载变化而变化，这 些变化将影响线性稳压器的稳定性，其输出电压不稳定。传统的低压差线性稳 压器需接容值较大的片外电容，使其性能稳定，可以快速响应瞬态变化。但增 加引脚意味着增加费用。无片外电容的低压差线性稳压需要增加特殊结构，用 来完成快速瞬态响应。该结构越简单越好，所需元件减少，直流功耗小；只改 善瞬态特性，不影响低压差线性稳压的直流特性。 1.2 研究内容及贡献 本文设计完成了带隙基准电压源电路、电压—电流转换电路和低压差线性 稳压器电路，各部分的相互关系如图 1-1 所示。 带隙基准电压源电路使用数字信号控制 PNP 双极型晶体管数目，调整输 出参考电压，进行修正，消除温度和工艺等产生的影响。选用合适的双极型晶 体管比值和电阻的比值，可以实现低噪声的输出电压。在输出端加 RC 低通滤 波器滤除高频噪声，高频性能得到改善。 电压—电流转换电路使用片外可调电阻，抵消工艺产生的偏差。输出电流 支路采用低电压共源共栅结构，该结构可以增加输出阻抗，输出的偏置电流更 准确。 低压差线性稳压器的设计中增加自动检测网络，在外界负载变化较大时