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# Category: Chapter 7 microelectronics by sedra and smith

# 5.2 Calculate the total charge stored in the channel of an NMOS transistor having Cox = 9 fF/μm2, L = 0.36 μm, and W = 3.6 μm, and operated at VOV = 0.2 V and V DS = 0 V.

# 5.1 MOS technology is used to fabricate a capacitor, utilizing the gate metallization and the substrate as the capacitor electrodes. Find the area required per 1-pF capacitance for oxide thickness ranging from 2 nm to 10 nm. For a square plate capacitor of 10 pF, what dimensions are needed?

# *2.127 In designing with op amps one has to check the limitations on the voltage and frequency ranges of operation of the closed-loop amplifier, imposed by the op-amp finite bandwidth (ft), slew rate (SR), and output saturation (Vomax). This problem illustrates the point by considering the use of an op amp with ft = 20 MHz, SR = 10 V/μs, and Vomax = 10 V in the design of a noninverting amplifier with a nominal gain of 10. Assume a sine-wave input with peak amplitude Vi. (a) If Vi = 0.5 V, what is the maximum frequency before the output distorts? (b) If f = 200 kHz, what is the maximum value of Vi before the output distorts? (c) If Vi = 50 mV, what is the useful frequency range of operation? (d) If f = 50 kHz, what is the useful input voltage range?

# 2.126 For an amplifier having a slew rate of 40 V/μs, what is the highest frequency at which a 20-V peak-to-peak sine wave can be produced at the output?

# 2.125 What is the highest frequency of a triangle wave of 10-V peak-to-peak amplitude that can be reproduced by an op amp whose slew rate is 20 V/μs? For a sine wave of the same frequency, what is the maximum amplitude of output signal that remains undistorted?

# 2.124 For operation with 10-V output pulses with the requirement that the sum of the rise and fall times represent only 20% of the pulse width (at half-amplitude), what is the slew-rate requirement for an op amp to handle pulses 2 μs wide? (Note: The rise and fall times of a pulse signal are usually measured between the 10%- and 90%-height points.)

# 2.123 An op amp having a slew rate of 10 V/μs is to be used in the unity-gain follower configuration, with input pulses that rise from 0 to 2 V. What is the shortest pulse that can be used while ensuring full-amplitude output? For such a pulse, describe the output resulting.

# 2.122 Consider an op amp connected in the inverting configuration to realize a closed-loop gain of −100 V/V utilizing resistors of 1 k and 100 k. A load resistance RL is connected from the output to ground, and a low-frequency sine-wave signal of peak amplitude Vp is applied to the input. Let the op amp be ideal except that its output voltage saturates at±10 V and its output current is limited to therange±20 mA. (a) For RL = 1 k, what is the maximum possible value of Vp while an undistorted output sinusoid is obtained? (b) Repeat (a) for RL = 200 . (c) If it is desired to obtain an output sinusoid of 10-V peak amplitude, what minimum value of RL is allowed?

# 2.121 A particular op amp using ±15-V supplies operates linearly for outputs in the range −14 V to +14 V. If used in an inverting amplifier configuration of gain −100, what is the rms value of the largest possible sine wave that can be applied at the input without output clipping?

# *2.120 Consider an inverting summer with two inputs V1 and V2 and with V o = −(V1+ 3V2). Find the 3-dB frequency of each of the gain functions Vo/V1 and Vo/V2 in terms of the op amp ft. (Hint: In each case, the other input to the summer can be set to zero—an application of superposition.)

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