Question

(a) Design the circuit (Find values for Rc, Rei and Rez) to amplify a 12mV sinusoidal signal from a microphone to a 0.4 V sinusoidal output signal, and make le = 0.2 mA. (20 points) (6) Draw complete small signal equivalent circuit of the amplifier. Clearly label all components. (Spoints) (c) Find values of input resistance (Rin), output resistance (Rout), and open circuit voltage gain ( Avo). (20 points) Assume B = 100, VBE.ON=0.7V, VA=00, and capacitors are very large (c). VT= 25mV at room temperature. Use Veesat = 0.2 V if necessary You must show all the steps. Explain your design strategy. Do not ignore base current (in #0). VCC 5.0V out

Answer 1

Question - given vin=12mv vout = 0.4u. vout = laufvin * go Au- gair of the Amp. II Avl = 04 = 33.33 12 mA given amplifier is the common Emmiter amplifier It work like as a inverter Hence I voltage gain = -33.33 1 Le oo = 100, VBE =0.7 , Ic = 0.2mA. IB = 0. 2mA = 24A. 100 DC Ac signal Analysis. o- short circuit the voltage $ capacitors B soules Ib + I hfe Ib vin {hie { = 12.5k2 rut 0 Slook =12562 looly hfe = B =100 ylithfe) 36 3 REI hie=nvy =25mv Tň zun hie=42.5ks kue of loop o vin = (hie + thfe) Rej) In CScanned with CamScanner

Vorut = hfe Ib: Rc O: I wount | = 33.33 - 1 - 100 Ib Rc TlO1RE, 22 Ib Rcx100 33. 33 = REI tot 10 12.5 |12,50 +101 Re, = 38 e+101 - Dc concelysis. 50- OVB-V6=0.7 VE = VB-0.7 VE =-0.2-0.7 Tue=-0.9 turn RETRE2 sv. do Io = O-VB lookz = 24A Je = BulIc - VB = -Qrioftros lol x 0.2 mA 100 =0. 202 m I UB=-0.2v] I VE-(-5)=0.202 ReitREZ - - 0.202 RE,TRE2 CSScanned with CamScanner Ret Re2=20.297 1

VB = -0.2, VE = -0.9 .. there are more variable to find. O amel Less equ. so we use Vesat = 0.2 Ve-VE = 0.2 Ne= 0.2 tue Vc= 0.2-0.9 = -0.7 I= 65-(-0.7) = 0.2mA. - Rc 5.7 =Rc o 2 mA [ Re=28.5ks from ean ② 12,5 + 101 RE, = 3 x 28.5 LRE,= 0.722 kr/ O RE, TRE 2 = 20.297 Reg. = 20.297 - RE ES$canned with CamScanner R42 = 19.57 ks canned with Cam |

summary :- (i) Re= 28.5kr (6) RE, = 0.722k2 (10) REZ 9.57 62 ② Draw the AC equivalent (small signal analysis ) "hie=312.56 k2 6 10036 vino {lookz {28.5ks vout ro Y10132. 30.72262 Frout. / pout. til hiettore, - Rin= loo|| Rin =+ 25 Rin= 100/185:42 oo kul in Loop ☺ vin - 12.5 Ib - 0-722x10135 30 | Rin=46.kz] for Rout. Rin - Yin - 12.5 +0.4228101 vin= shorckt. 3650 =) Rout = 28.5kr Rin = 85.42. | Aih = -33.33 alreuety solved in "@"Part o sign show that common Emmitter CSScanned with CamScanner Amp. always like an inverter