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Question: solve 34...

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259 ANSWERS TO REVIEW QUESTIONS 20 mV RG 1.0 MQ, IG sat 1.0kΩ CONTROL FIGURE 4-71 FIGURE 4-72 ■ ANSWERS Section 4-1 TO REVIEW QUESTIONS 1. Drain, source and gate 2. MOSFET 3. They require smaller areas than BJTs, are easy to manufacture in ICs, and produce simpler cir- cuits 4. BJTs s are controlled by a current, FETs are controlled by a voltage. BJT circuits have higher gain but lower input resistance. Section 4-2 1. Transconductance curve 2. Positive 3. By the gate-to-source voltage 4. 7 V 5. Decrease 6. +3 V Section 4-3 1. Vasfof) and Ipss. 2. The base-emitter pn junction in a BJT is forward biased; the gate-source pn junction in a J FET is reverse biased. 3.-8 V 4. Ipss Section 4-4 1. Depletion MOSFET and enhancement-only MOSFET. The D-MOSFET has a physical channel; the E-MOSFET does not. 2. Yes; the current is IDss- 3. No 4. Yes258 FIELD-EFFECT TRANSISTORS (FETs) 29. Assume the amplifier in Figure 4-69 has no output voltage. A check of the dc c 30. Refer to Figure 4-69. Assume the dc voltages and the ac input voltage are correct, br vai, is 31. Refer to Figure 4-69. What is the minimum value of lpss that Q, can have before the gate- 32. Assume the source voltage for the D-MOSFET in Figure 4-70 is measured and that the drain voltage is 15 V. Name at least three failures that can account for this. very small. What failure can account for this? source pn junction is forward-biased? to be 1.6 V (a) Compute Ip and Vos (b) If gs. 2000 ㎛ho, what is the voltage gain? (c) Compute the input resistance of the amplifier. (d) Is the D-MOSFET operating in the depletion or the enhancement mode!? e) Compute Vout FIGURE 4-70 +24V 5.1 ΜΩ 0.1μF 0.1μF 100mV pp 1.0 kHz Rs 330 2 C2 33 HF 10ΜΩ 33. Repeat Problem 32 (a) and (b) if a 5.1 kl2 load is connected between Vour and 34. Assume Q, and Q2 in Figure 4-71 have matching characteristics and Ipss is 1.5 mA. (a) What is ID? (b) What is the approximate gain? (e) If 02 is replaced with a transistor with an Iss of 1.0 mA, what problem will oc SECTION 4-7 FET Switching Circuits 35. Explain why rps(on) is one of the most important specifications for an analog switch 36. The 2N5555 is an n-channel JFET switching transistor. The specification Of 2.0 μΑ -10 V at a temperature of 100°C, Assume it is used in the analog switch circuit of (on)(max > = 150 Ω and IDSStnie) = 15 mA. It also shows a maximum drain VGS Figure 4-72 for the worst case conditions given here. (a) What is the output voltage when Vas V (b) What is the output voltage when Vas-10 V? 37. What are the two operating conditions for a transistor in a digital switch called? 38. CouldaD-MOSFET be substituted for the E-MOSFET in Figure 4-51(c)? Explain your answen

Solve 34.

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