两级放大电路的设计(供参考).docx
设计指标：Av>250, 7?i>10kQ, RL=5.lkQ, BW=50Hz50kHz, D<5%。设计条件：输入信号（正弦信号）：2mVS%S5mV,信号源内阻：&=50。，电源电压：Vcc=12V；半导体三极管 9013,参数：4=100, Fbb=300Q, O=5pF,-=150MHz, 3V<Vcc<20V, PcM=625mW, /cM=500mA, V（br）ceo=40V。1 .电路选型：小信号放大电路选用如图1所示两级阻容耦合放大电路，偏置电路采用射极偏置方 式，为了提高输入电阻及减小失真，满足失真度D<5%的要求，各级射极引入了交流串 联负反馈电阻。2 .指标分配：要求Av250,设计计算取Av=300,其中Ti级Avi=12, Av2=25； RiNlOkQ要求较高, 一般，E级需引入交流串联负反馈。3 .半导体器件的选定指标中，对电路噪声没有特别要求，无需选低噪声管；电路为小信号放大，上限频 率,/k=50kHz,要求不高，故可选一般的小功率管。现选取NPN型管9013,取用=100。4 .各级静态工作点设定动态范围估算：级：曦|=回皿=5血111耳4=12, 嗑i=AMmi=12x5 = 84mV。T2 级：Km2= Kml= 84mV , AV2 = 25 ,Xm2= A2Km2 =25X84 = 2. IV o为避免饱和失真，应选：CcEQL+%（sat）；可见T1级VCEQI可选小些，T2级VCEQ2可选大些。，CQ取值考虑：设定主要根据，CQ之，CM +，CEQ，由于小信号电压放大电路，CM较小;另从减小噪声及降低直流功率损耗出发，Tp工作电流应选小些。Ti级静态工作点确定:取乐N 3kQ,依=诲'+，在，可推得 ，CQ1/ 二 0%其中/ = 100, %= 300,%=26mV可求得L V -NG=0.963mACQ, 3000-300选 ZCQ1 = 0.7mA，/bqi =等=007mA , VCEQ1 = 2V>0.12VT2级静态工作点确定:一般应取小>汨 'Yzeq2 > Yzeqi选：Icm= 1,2mA , /RO9= 0.012mA , VCFO9 = 4V>3VL-Q2707。匕 QN5 .偏置电路设计计算（设Keq=07V）1级偏置电路计算:WRbl =10/BQ1 =10x0.007 = 0.07mA% =4x12 = 4VI 33故：7?bl =% ="心=114.2861<。取标称值 120 kQbl /bl 0.07% = /bl2/?bI = 0.072 x 120 = 0.588mW<-W 选 " 120kQ Jw88= BQ1 = - = 63.492kQ 取标称值 62 kQ/Rb?，Rhi /rch0.07 0.007 0.063KDZKdI bqi选 62 kQ/-W84b2 =后&2 = 0 0632 x 62 = 0.246mW< - W8BQi BEQI _ Kq1 KeQI _ 4 0.7EQI(1 + )/bqi101x0.07 0.707=4oi2r =0.7072x0.3 = 0.15mW<-WIxC 11 C1P , =/ ?/? , =0.7072 x 4.7 = 2.15mW<iwKC1CQZ C1g选&' 300Q/-W选尺/4.3koJw88=匕 c=匕 c%eq（Kqeqi）= 12-2-4 + 0.7 = 9,57 k。，CQ1取标称值9.lkQci = Qici =0.72x9.1 = 4.46mW<|w 选跖 9.1 kQ/|wT2级偏置电路计算:取几3 =10幅3 =10x0012 = 0.12mA小 小cgl2 = 4VsVcc -12-4取标称值68 kQ故： R -_221 = 66.67kQI 0 12，Rb34b3 = L32Hb3 = 0. 122 x 68 = 0.979mW<W选仆 68 kQ J W88R = "21 = _3 =i= 37.04kQ 取标称值 36 kQ4b4 L ，bq2 0-12-0.012 0.108h4 =4m24 =0.1082x36 = 0.42mW<-W 选 36 kQ/-W IxD4tKDQ OH-汁r _ Kq2 - Keq2 _ %Q2 - %eq2 _ 4 一 °7 _ 3.3 _ ? 723kQe2 -7Z - （l+/?）/RO? - 101x0.012 - 1.212 - .凡2分为62'（交流负反馈）、&2”，取"2' = 56d R/ = 2.7kC4c2' = /EQ22/?c2. =1.2122x0.056 = 0.082mW<iw 8%优=&2, = 1.2122 x 2.7 = 3.97mW<iw选Re2 56Q/iw 选2" 2. 7kQ/-W 88A =匕c-%EQ2-%Q2 = 12-4-4 + 0.7 = 3 92ko取标称值 3.9kQ小21.2%2 = %Q；Rc2 = 1灸 x3.9 = 5.62mW<-W 选 RC2 3.9 kQ /-W886 .静态工作点的核算Ti级:r :r% 一BEQl xl2-0.7/CO1= 100x 热 +黑=0.67mACQ， BQ，"时心+(1 + 0&120x62+101x4 6120 + 62匕EQI = %-(1 + 0%(=12-0. 67x9. l-101x匕x4.6 = 2.79V100符合设计要求。4-V -VrCC VBEQ2b3 b4二 100x43&4+(1+/)62360八x 12 - 0.7/叶 36= 1.144mA68x36 3+ 101x2.75668 + 36匕EQ2 -Q +为母421 144=12-1. 144x3. 9-101x-x2.756 = 4.354V100符合设计要求。7 .电容器的选择Ci：噎二就,+ 夕当_ = 300 +100 x = 4.18kQ；cqi。67二受空= 40.88kQR，=R R bl bzKJ =噎 + (I + 0)R°，=4.18 + 101x0.3 = 34.48kQ120 + 6240,88x34.48 87kQ4'+扁'40.88 + 34.48Rs =50QG之(310)2祉(4+尺)=(3 10)x271X 50 X (0.05+18.7) X103= (310)xL7 = 5.l|iF17|iF取 G =10piF选 G 10iF/16VC2：R。 RC = 9.1kQv26小=/ +_!_ = 300 +100 x= 2.573kQbe2 bb21014442'=展2 +(1 + 仍R&= 2.573 + 101x 0.056 = 8.23kQG 2 (3 10)68x36 “368 + 3623.54x8.23 , 1n 八=6.1kQ2.54 + 8.2312胡L (凡I +凡)=(3 10)x27tx50x(9.1+6.1)xl03=(3 10) X 1.99 = 5.97|1F19.9|iFC3：取=1。好选 C2 10|iF/16VG >(3-10)2班(62+七)= (3-10)x2兀 x 50x(3.9+5.1)x103(3-10)x3.54 = 10.62四35.4(iF取。3 = 10)iF选 G 10|iF/16VCel：27ix50x4.3xl03=(3 10) x 7.4 = 222(iF74|iF取 Cei=47|jF 选 Cd 47|JF/16V271x50x2.7x1()3”媪L"°)x取 Ce2=47|jF 选 Ce2 47|jF/l 6V8 .指标核算Ri=18.7k Q >10k Q 满足设计要求%二兄2=6. Ik Q9 1x6=&凡- = 3.652kQL1七9.1 + 6.1鼠=4& = _100x* = TlV1与 34.483 9x5 1R=二- = 2.21kQl 9 l 3.9 + 51R2 21Av? = -lOOx = -26.85V2Rn8.23v = 4 A；2 = T1 x (-26.85) = 295 > 250 满足设计指标要求。核算/h、/l：A：Q = (Rs + RJG = (0.05 + 18.7)x103x10x10-6=1 87.5ms卬=心个广+冗)/&0所今*+凡)氏00342x43 xlO3x47xIO" = 14.89ms0.342 + 4.3% =(% + &)Q =(9. 1 + 6. 1) x 1 ()3 x 10 x 10" = 152msX心/我常+小+凡)心Q=0.146义2.7 X03 *47x 10-60.146 + 2.7=0.139 x 103x 47 x 10-6 = 6.51ms- + + )xlO3 14.89 152 6.51/ 1kl 1/12k2”115 4乙 271x1.15 187.5=32.2Hz < 50Hz满足设计要求/h :口 二 44ms 26gml"V/J V/111乙Tm = R40cm =191.224 x103x5xWI2 = 0.956|is1.151.15 , 142 Tlz *Hjj=l2ti 0.5166 1.656 0.2886 0.956/CQ1 0.67 y F- = 25.77msVT 26Ri " A + 碗 +(1 + M,l =霏;煞 x 1。3 二 3.444m = 3.444 xl03x 150 xW12 =0.5166|isA； =-& =-25.77x3.652 = 94.112R = R (1 + g R ) + R = 3.444X 1()3X95 112 + 3.652xlO3 =331.218kQ /U1 U* 1111 JU/ 1JL-/1/H2 =尺2。&1 = 331.218 X1 ()3 x 5 x 10-2 = 1 65611s&o = Rc/ A + 欣 + (1 + 0凡%=：；：X1。3 = 1.924kQ7H3 = R30c兀2 =1924义 1()3x150 X10-2 =0 2886|is42= -gm2/?L =-44x2.21 = -97.247?4O =凡0(1 +?) + R，= (L924 x 98.24 + 2.21)xl03= 191.224kQ=53.56kHz > 50kHz满足设计要求
