电工习题3

1. 1. Consider the circuit of Figure 1 where R 1=R 2=1Ω and R 3=2Ω. Find the three currents, i 1,i 2, i 3.2. 2.find the current I throughthe 10V voltage source for the circuit shown in Figure 2.3. 3. The circuit shown in Figure 3 has two sources: v s =20cos(105t+90︒) V and i s =6cos105t A.Determine v o (t).4. 4.thecircuit ofFigure 4.5. 5. Design a series resonant circuit to have Ω== 100/1)Y ( rad/s, 250000ωω, andrad/s 500=BW .6. 6. A Y-connected source and load are shown in Figure 6. (a) Determine the rms value of thecurrent i a (t ) . (b) Determine the average power delivered to the load.7.R 3 Figure 1 Ω Ω Figure 2 v Figure 3 L (t)Figure 4v ab (t) + _v s Figure 58. The circuit shown in Figure 8 is at steady state before the switch closes at time t=0s. The switch remains closed for 1.5s and then opens. Determine the inductor current, i L (t), for t>0s.9.For the circuit of Figure 9, specify the value of the resistance R L that will cause current i L to be –2A.10. Find v x (t) by first replacing the circuit to the left of terminals a-b in Figure 10 with itsThevenin equivalent circuit when C=2500μF.11. Consider the meter indications in each circuit of the Figure 11, and determine whether the diode is functioning properly, or whether it is open or shorted.i LL Figure 9 -2v + v x Figure 1068Ω68Ω12.Assume that a 600 Ω, 12 μV rms voltage source is driving the amplifier in Figure 12. Determine the overall voltage gain by taking into account the attenuation in the base circuit, and find the total output voltage (ac and dc). What is the phase relationship of collector signal voltage to the base signal voltage?13.A load resistance isIn terms of signal14.15.16.Find the value of R fFigure 16Figure 12 V CC V in L Ω Figure 13 V out V CC V in V in V DD R L Ω Figure 15R f V in (a) R f V in (b)V OUT 1 V +1.8 V17.(a)Find the overall voltage gain of the instrumentation amplifier in Figure 17.V in 1=5 mV, V in 2=10 mV , and V cm ). Determine the final outputvoltage.(c)What value of R G must be used to change the gain of the instrumentation amplifier in Figure1 to 1000?18. Determine the output voltage waveform in Figure 18.19.(1)What type of signal does the circuit in Figure 19 produce? Determine the frequency of the output.(2)Show how to change the frequency of oscillation in Figure 3 to 10 kHz.20. Find the maximum signal power achievable with the class B push-pull amplifier in Figure 20. Find the dc input power.Answer: W 98.3 W;13.3==DC out P PFigure 18V out2 Ω V in3 Ω+3V 0 - 3 VV out(max)= ± 10 VFigure 19 18 k ΩV out V in V in 2 V out V inV CC21. Consider the circuit in Figure 21.(a) (a) What type of circuit is this?(b) (b) What is the total peak secondary voltage?(c) (c) Find the peak voltage across each half of the secondary. (d) (d) Sketch the voltage waveform across R L .(e) (e) What is the peak current through each diode?(f) (f) What is the PIV (PIV , 反向峰值电压) for each diode?22. Sketch the outputthat all the diode are reversed from previous circuits.23.(a)Using Boolean algebra techniques, simplify the following expression as much as possible:D C B A C B A C B A ++++(b)Use a Karnaugh map to simplify the following expression to a minimum SOP form (SOP form, sun-of-product form, 积和式，与或式)： ABCD D C B CD D C B A B A ++++(c)Reduce the function specified in the truth table in Figure 23 to its minimum SOP form byusing a Karnaugh map.24. As you have learned, the two logic symbols shown in Figure 24 represent equivalent operations. The difference between the two is strictly from a functional viewpoint. For the NAND symbol, look for two HIGHs on the inputs to give a LOW output. For the negative-OR, look for atX2Figure 24A BΩL Figure 21 V out Figure 22least one LOW on the inputs to give a HIGH on the output. Using these two functional viewpoints, show that each gate will produce the same output for the given inputs.25. For the 4-bit comparator in Figure 25, plot each output waveform for the inputs shown. The outputs are active-HIGH.26. Sketch the Qoutput relative to the clock for a D flip-flop with the inputs as shown in Figure 26. Assume positive edge-triggering and27. Determine the Q output in Figure 27. Assume that Q is initially LOW.28. By analyzing the J and K inputs to each flip-flop prior to each clock pulse, prove that the decade counter in Figure 28 progresses through a BCD sequence. Explain how these conditions in each case cause the counter to go to the next proper state.Figure 28Figure 25 A 3 A 0 A 2 A 1 B 3 B 0 B 2 B 1 V 74HC85A A A AB B B B Figure 26Figure 2729.The waveforms in Figure 29 are applied to a 74HC163（引脚功能同74LS163） counter. Determine the Q outputs and the RCO (即Q CO ). The inputs are ,0,1,1210===D D D and 13=D .30.For each of the cascaded counter configurations in Figure 30, determine the frequency of the waveform at each point indicated by a circled number, and determine the overall modulus.31.for the analog input signal in Figure 31. The sampling rate is 100 kHz.（A/D 参考电压V R＝9V ）V t(μs )Figure 31Figure 30 18 MHz (b) (a)(c) Figure 2932. To what value must the variable resistance be adjusted in figure 32 in order to turn the SCR off? Assume I H =10 mA and V AK =0.7 V .33. Sketch the V Rinput waveforms.34.I H =1 mA.35.Xs represent intact fusible links.36. 36.an on cell.V R V A V Figure 34V A V G 15 V peakRΩ Figure 32R IXFigure 35Figure 36。