Problem 1Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answer without an outline of the solution. A mish-mash of calculations is not an acceptable outline. Problem 2Problem 3Problem 4Problem 5Problem 6ECE 304 Final Exam Spring `04 11 AM – 1PM Closed Book NOTE: In all cases 1. Put your answer first, and 2. Follow up with an outline of your solution. Each major step in the outline should 2.1. Begin with a heading that describes the objective of that step, and should 2.2. Have a body where actual work is done, not just hand waving, and should 2.3. Conclude with a quantitative statement of the major result for that step (a number or formula or both). For all problems take the thermal voltage as VTH = 25.864 mV. Problem 1 -++-E3GAIN = -1E3+{R1}+{R2}+{C2}-++-E1GAIN = -1E3+Rload1k+{R3}ACSweepIS1A+-G1000PARAMETERS:C1 = 1uFC2 = 1nFC3 = 100pFR1 = 1kR2 = 1kR3 = 1kBfb=1.25E-8 A/V0+{C3}+{C1}0-++-E4GAIN = 1+Rin1k-++-E2GAIN = -1E3 V1 V3IN V2 OUTFIGURE 1 Three-pole amplifier in a feedback circuit For the circuit of Figure 1 select a new value of C1 so the amplifier operates with a phase margin of 45° when the feedback βFB = 1.25 × 10–8 A/V. All resistors are 1 kΩ, and the gains of VCVS E1, E2, E3 are –103 V/V. The last VCVS E4 has unity gain. The feedback VCCS has a gain βFB = 1.25 × 10–8 A/V. Capacitor C2 = 1 nF, C3 = 100 pF. For the given values of R and C the pole frequencies are f1 = 159.15Hz, f2 = 159.15 kHz, and f3 = 1.5915 MHz. Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answer without an outline of the solution. A mish-mash of calculations is not an acceptable outline.Unpublished work © 2004 John R Brews Page 1 5/6/2004Problem 2 +RB1k-++-E2GAIN = 1E3+RC1k0+RA1k0+Ro 1k+-VDC1V+Ri1k0+RL1k OUTINFIGURE 2 Feedback amplifier; gain of main stage from part E2 is 1000V/V In Figure 2 all resistors are 1 kΩ and the main amplifier has a gain of 1kV/V. 1. Determine the gain of the amplifier with feedback and its units. 2. State which resistors could be eliminated from the feedback T-section and say why. Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answer without an outline of the solution. A mish-mash of calculations is not an acceptable outline. Unpublished work © 2004 John R Brews Page 2 5/6/2004Problem 3 +-V4-15V+-V115VQidealNQ1+R41k0+R21k+R31k0QidealNQ3+-VIN-150.model QidealN NPN (Bf=100,Is=10fA}QidealNQ20+R11k INOUTFIGURE 3 Voltage follower stage For the circuit of Figure 3, determine the DC value of VOUT for a DC input voltage of VIN = –15V. Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answer without an outline of the solution. A mish-mash of calculations is not an acceptable outline. Unpublished work © 2004 John R Brews Page 3 5/6/2004Problem 4 +R11+-VIN15VOUTVP00.model QPWRp PNP (Bf=30,Is=100fA).model QPWRn NPN (Bf=30,Is=100fA)VPVN.model QidealN NPN (Bf=100,Is=10fA}+-V215V+-V3-15V+R21kVNQPWRnQNQPWRpQPVPIN0I1100mA0 FIGURE 4 Power output amplifier For the circuit of Figure 4, determine the DC value of VOUT when the DC value of VIN = 15 V. Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answer without an outline of the solution. A mish-mash of calculations is not an acceptable outline. Unpublished work © 2004 John R Brews Page 4 5/6/2004Problem 5 +-V315V+R2800+-VA1V0+R31k+-VB1V.model QidealN NPN (Bf=100,Is=10fA}QidealNQB+R1800000QidealNQA+-V4-15V OUTBOUTABA BBE FIGURE 5 Differential amplifier For the amplifier of Figure 5 assume the maximum forward bias of the CB junction in saturation is VCB = –VSAT = –600 mV. Also, assume in active mode VBE = 700mV. Make a table like the one below and fill it in. Do NOT use the table on this page. Mode Mode VAVB QAQB VOUTAVOUTB VE71211101 Provide an outline only for the case VA = 2V. For this case, follow the outline procedure at the top of the exam with headings for each major step in the solution. A mish-mash of calculations is not an acceptable outline. Unpublished work © 2004 John R Brews Page 5 5/6/2004Problem 6 +Cpi50pFQidealPQ1VDB+R21k00ACSweepIac1A+Cmu2pF0.model QidealP PNP (Bf=100,Is=10fA)+-V1-15V0+R1100IDC10mA INOUTFIGURE 6 Transresistance amplifier In Figure 6 the transistor parasitic capacitances Cpi ≡ Cπ and Cmu ≡ Cµ are shown explicitly as if they were external capacitances with values Cπ = 50 pF and Cµ = 2 pF. Determine the upper 3dB corner frequency of the small-signal transresistance gain Vout/Iac. Follow the outline procedure at the top of the exam with headings for each major step in the solution. No points for answers without an outline of the solution. A mish-mash of calculations is not an acceptable outline. Unpublished work © 2004 John R Brews Page 6