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Category: microelectronics by sedra and smith

Category: microelectronics by sedra and smith

10.71 Find the dc gain and the 3-dB frequency of a MOScascode amplifier operated at gm = 2 mA/V and ro = 20 k.The MOSFETs have Cgs = 20 fF, Cgd = 5 fF, and Cd b = 5 fF.The amplifier is fed from a signal source with Rsig = 100 kand is connected to a load resistance of 1 M. There is alsoa load capacitance CL of 20 fF.

10.71 Find the dc gain and the 3-dB frequency of a MOScascode amplifier operated at gm = 2 mA/V and ro = 20 k.The MOSFETs have Cgs = 20 fF, Cgd = 5 fF, and Cd b = 5 fF.The amplifier is fed from a signal source with Rsig = 100 kand is connected to a load resistance of 1 M. There is alsoa load capacitance CL of 20 fF.

10.70 An IC CG amplifier is fed from a signal source withRsig = ro/2, where ro is the MOSFET output resistance. It has acurrent-source load with an output resistance equal to ro. TheMOSFET is operated at ID = 100 μA and has gm = 1.5 mA/V,VA = 10 V, Cgs = 0.2 pF, Cgd = 0.015 pF, and Cd b = 20 fF.As well, the current-source load provides an additional 30 fFcapacitance at the output node. Find fH .

10.70 An IC CG amplifier is fed from a signal source withRsig = ro/2, where ro is the MOSFET output resistance. It has acurrent-source load with an output resistance equal to ro. TheMOSFET is operated at ID = 100 μA and has gm = 1.5 mA/V,VA = 10 V, Cgs = 0.2 pF, Cgd = 0.015 pF, and Cd b = 20 fF.As well, the current-source load provides an additional 30 fFcapacitance at the output node. Find fH .

10.69 For the CG amplifier in Example 10.9, how muchadditional capacitance should be connected between theoutput node and ground to reduce fH to 200 MHz?

10.69 For the CG amplifier in Example 10.9, how muchadditional capacitance should be connected between theoutput node and ground to reduce fH to 200 MHz?

10.68 Consider a CG amplifier loaded in a resistance RL = roand fed with a signal source having a resistance Rsig = ro/2.Also let CL = Cgs. Use the method of open-circuit timeconstants to show that for gmro 1, the upper 3-dB frequencyis related to the MOSFET fT by the approximate expression

10.68 Consider a CG amplifier loaded in a resistance RL = roand fed with a signal source having a resistance Rsig = ro/2.Also let CL = Cgs. Use the method of open-circuit timeconstants to show that for gmro 1, the upper 3-dB frequencyis related to the MOSFET fT by the approximate expression

*10.67 Sketch the high-frequency equivalent circuit of a CBamplifier fed from a signal generator characterized by Vsigand Rsig and feeding a load resistance RL in parallel with acapacitance CL.

*10.67 Sketch the high-frequency equivalent circuit of a CBamplifier fed from a signal generator characterized by Vsigand Rsig and feeding a load resistance RL in parallel with acapacitance CL.

10.66 A CG amplifier is specified to have Cgs = 4 pF, Cgd =0.2 pF, CL = 2 pF, gm = 5 mA/V, Rsig = 1 k, and RL =10 k. Neglecting the effects of ro, find the low-frequencygain Vo/Vsig, the frequencies of the poles fP1 and fP2, and hencean estimate of the 3-dB frequency fH .

10.66 A CG amplifier is specified to have Cgs = 4 pF, Cgd =0.2 pF, CL = 2 pF, gm = 5 mA/V, Rsig = 1 k, and RL =10 k. Neglecting the effects of ro, find the low-frequencygain Vo/Vsig, the frequencies of the poles fP1 and fP2, and hencean estimate of the 3-dB frequency fH .

10.65 Use the method of open-circuit time constants tofind fH for a CS amplifier for which gm = 1.5 mA/V, Cgs =Cgd = 0.2 pF, ro = 20 k, RL = 12 k, and Rsig = 100 kfor the following cases: (a) CL = 0, (b) CL = 10 pF, and (c)CL = 50 pF. Compare with the value of fH obtained using theMiller approximation.

10.65 Use the method of open-circuit time constants tofind fH for a CS amplifier for which gm = 1.5 mA/V, Cgs =Cgd = 0.2 pF, ro = 20 k, RL = 12 k, and Rsig = 100 kfor the following cases: (a) CL = 0, (b) CL = 10 pF, and (c)CL = 50 pF. Compare with the value of fH obtained using theMiller approximation.

10.64 Consider a CS amplifier loaded in a current sourcewith an output resistance equal to ro of the amplifyingtransistor. The amplifier is fed from a signal source with Rsig =ro/2. The transistor is biased to operate at gm = 2 mA/V andro = 20 k; Cgs = Cgd = 0.1 pF. Use the Miller approximationto determine an estimate of fH . Repeat for the following twocases: (i) the bias current I in the entire system is reduced bya factor of 4, and (ii) the bias current I in the entire systemis increased by a factor of 4. Remember that both Rsig and RLwill change as ro changes.

10.64 Consider a CS amplifier loaded in a current sourcewith an output resistance equal to ro of the amplifyingtransistor. The amplifier is fed from a signal source with Rsig =ro/2. The transistor is biased to operate at gm = 2 mA/V andro = 20 k; Cgs = Cgd = 0.1 pF. Use the Miller approximationto determine an estimate of fH . Repeat for the following twocases: (i) the bias current I in the entire system is reduced bya factor of 4, and (ii) the bias current I in the entire systemis increased by a factor of 4. Remember that both Rsig and RLwill change as ro changes.

10.63 A common-emitter amplifier has Cπ = 10 pF, Cμ =0.3 pF, CL = 3 pF, gm = 40 mA/V, β = 100, rx = 100 ,RL = 5 k, and Rsig = 1 k. Find the midband gain AMand an estimate of the 3-dB frequency fH using the Millerapproximation. Also, obtain another estimate of fH usingthe method of open-circuit time constants. Which of thetwo estimates would you consider to be more realistic,and why?

10.63 A common-emitter amplifier has Cπ = 10 pF, Cμ =0.3 pF, CL = 3 pF, gm = 40 mA/V, β = 100, rx = 100 ,RL = 5 k, and Rsig = 1 k. Find the midband gain AMand an estimate of the 3-dB frequency fH using the Millerapproximation. Also, obtain another estimate of fH usingthe method of open-circuit time constants. Which of thetwo estimates would you consider to be more realistic,and why?

10.62 Consider the CE amplifier whose equivalent circuit isshown in Fig. 10.19(a) but with a capacitance CL connectedacross the output terminals. Let R

10.62 Consider the CE amplifier whose equivalent circuit isshown in Fig. 10.19(a) but with a capacitance CL connectedacross the output terminals. Let R

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