MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Electrical Engineering and Computer Science 6 002 Electronic Circuits Fall 2004 Homework 7 Handout F04 037 Issued 10 21 2004 Due 10 29 2004 Helpful Readings for this Homework 8 2 9 1 10 1 10 3 Exercise 7 1 a Exercise 9 1 p 691 b Repeat part a with capacitors replaced by inductors Take the value of each inductor in mH to be numerically equal to the value of the capacitor it replaces in F Exercise 7 2 Exercise 10 16 p 800 Exercise 7 3 Exercise 10 22 p 804 Problem 7 1 VS VS R R vI vO vMID A two stage non inverting MOSFET amplifier is shown above In this problem VI is chosen such that V I V MID V O a Show that the input bias VI for which V I V MID V O is given by 1 1 2KR V S V T V I V T KR b Draw the small signal circuit for the amplifier and use it to determine the v v in out small signal gain G Express G as a function of K VT VI and R Problem 7 2 Problem 10 22 p 826 Assume that the capacitor is initially at zero volts Problem 7 3 VS vI i R vI L vDS Vo VT t T L R K 2 i DS v GS V T 2 The circuit shown is used to pulse the current in the coil of a relay modeled by the inductor L The design is such that the relay contacts close when the current reaches 70 of its steady state value i e the value reached at the time T L The resistor R R is placed in parallel with the relay coil L to limit transient voltages when the MOSFET is switched off a Assume that the MOSFET operates in the saturation region for 0 t T Determine and sketch i t and v DS t indicating clearly the waveforms for t 0 0 t T and T t b For the case examined in part a what limit must be placed on the maximum coil current if the MOSFET is required to stay in the saturation region for 0 t T Express the answer in terms of VS R K VT and Vo c For the case examined in part a what limit must be placed on the coil current if the maximum value of vDS is limited to 1 5Vs
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