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# Tag: voltage gain

# Question 3 Consider the following circuit shown below. You are required to design the bias stable circuit with small signal voltage gain close to Av = 10. Consider There is no Early effect.

# *10.106 Figure P10.106 shows an amplifier formed bycascading two CS stages. Note that the input bias voltageis not shown. Each of Q1 and Q2 is operated at an overdrivevoltage of 0.2 V, andVA= 10 V. The transistor capacitancesare as follows: Cgs = 20 fF, Cgd = 5 fF, and Cd b = 5 fF. Thesignal-source resistance Rsig = 10 k.(a) Find the dc voltage gain.(b) Use the method of open-circuit time constants todetermine an estimate for the 3-dB frequency fH

# *10.44 The amplifier shown in Fig. P10.44 hasRsig = RL = 1 k, RC = 1 k, RB = 47 k, β = 100,Cμ = 0.8 pF, and fT = 600 MHz. Assume the couplingcapacitors to be very large.(a) Find the dc collector current of the transistor.(b) Find gm and rπ .(c) Neglecting ro, find the midband voltage gain from baseto collector (neglect the effect of RB).(d) Use the gain obtained in (c) to find the component of Rinthat arises as a result of RB. Hence find Rin.(e) Find the overall gain at midband.(f) Find Cin.(g) Find fH

# 10.41 The amplifiers listed below are characterized by thedescriptor (A, C), where A is the voltage gain from input tooutput and C is an internal capacitor connected between inputand output. For each, find the equivalent capacitances at theinput and at the output as provided by the use of Miller’stheorem:

# 10.28 An ideal voltage amplifier having a voltage gain of–1000 V/V has a 0.2-pF capacitance connected between itsoutput and input terminals. What is the input capacitanceof the amplifier? If the amplifier is fed from a voltagesource Vsig having a resistance Rsig = 1 k, find the transferfunction Vo/Vsig as a function of the complex-frequencyvariable s and hence the 3-dB frequency fH and the unity-gainfrequency ft .

# 10.26 In a particular common-source amplifier for which themidband voltage gain between gate and drain (i.e., −gmRL)is −39 V/V, the NMOS transistor has Cgs = 1.0 pF andCgd = 0.1 pF. What input capacitance would you expect? Forwhat range of signal-source resistances can you expect the3-dB frequency to exceed 1 MHz? Neglect the effect of RG.

# 10.30 For the CC–CB amplifier of Fig. 10.41(a), let I = 0.5 mA, β = 100, Cπ = 6 pF, Cμ = 2 pF, Rsig =10 k, and RL = 10 k. Find the low-frequency overall voltage gain AM , the frequencies of the poles,and the 3-dB frequency fH . Find fH both exactly and using the approximate formula in Eq. (10.164).

# 10.29 Consider a CS amplifier having gm = 2 mA/V, ro = 20 k, RL = 20 k, Rsig = 20 k, Cgs = 20 fF,Cgd = 5 fF, and CL = 5 fF. (a) Find the voltage gain AM and the 3-dB frequency fH (using the methodof open-circuit time constants) and hence the gain–bandwidth product. (b) Repeat (a) for the casein which a resistance Rs is connected in series with the source terminal with a value selected so thatgm Rs = 2 .

# |. (25 points) Consider the following circuit. Ryy=5 k82, Ri=33 k8, R2=22kQ, Re=3.9kQ, Re=4.7kQ, Ri=5.6kQ, Vec=S5V. Also her=120, Va=60V, and r.=509. (a) (15 points) Find the midband voltage gain, input and output resistances. (b) (5 points) If fo1=/p3=10 Hz and fp2=100 Hz, estimate the lower 3-dB frequency /.. (c) (5 points) If required fi. is to be less than 50 Hz, find the smallest Cr.