EE 2212

PROBLEM SET 6

S. G. Burns

Due: Wednesday, 17 March 2021

NOTE 1: Table 4.6 on Page 203 provides useful generic FET specifications information. If these data are not provided in any of the Chapter 4 text problems, use information in Table 4.6. Also the inside of the front cover has all sorts of useful data. Just below Table 4.6 on Page 203, you will also find some key constants; also on the inside of the front cover.

NOTE 2: I also want to call your attention to the following link from our WEB page

FETNMOSSummary.tif FETPMOSSummary.jpeg

NOTE 3: Be sure your WEB browser displays symbol font correctly.

1. Text Problem 4.1 (Look at Figure 4.2 for guidance) and Text Problem 4.2 as a combination. For Text 4.2 observe that you are computing Cox, capacitance per unit area. Watch your units. Usually farads/cm² (cgs system) is preferred for the capacitance per unit area units. When the text and in the industry talks about an MOS capacitor, they are usually referring to capacitance/unit area. The total capacitance can then be scaled by multiplying by (W x L). Refer to Monday, 5 and 10 March PPTs. This idea of scaling is a very important VLSI design concept. The parallel plate basic capacitor model works well! We will also soon observe how this plays into imaging and display applications.

2. Text 4.4 and 4.8 for NMOS and Text 4.47 for PMOS. Plug and Chug. Some additional basic calculations to provide experience in units and nomenclature. Organize your results in a table. Page 160 (NMOS) and 161 (PMOS) has a table defining the relationships for key FET model parameters. Refer to the WEB links in Note 2.

3. Extracted from an old quiz. Regions of operation are very important in circuit design using MOSFETS. For the indicated bias conditions, state whether the FET is operating in the OHMIC (TRIODE) region, SATURATION region, or CUTOFF region. Explain your reasoning. Assume that |V_T | = 2 volts for both the NMOS and PMOS enhancement mode transistors. Arrow in for NMOS; arrow out for PMOS!!! M1 __________ M2 __________ M3 __________

M4 __________ M5 __________ M6 __________

4. Versions of this problem have also been extracted from old quizzes. Refer to the sketch of an n-channel enhancement-mode MOSFET fabricated in silicon. Assume room temperature operation. Also assume l = 0. Units are important. (a) through (d) are a modest sample of what could asked about the operation and physics of the NMOS and PMOS on a quiz. (Subtle Hint!!!)

(a) Compute a value for C_ox .

(b) Compute a value for the threshold voltage, V_t using the threshold voltage graph posted on the WEB page. ThresholdVoltageChart.JPG Assume W/L = 10 and make reasonable assumptions and/or use values from Table 4.6 for any other physical parameters you may need. Compute values for “k” and “KP” and then use your results from this part and Parts (a) and (b) to generate a Shichmann-Hodges Level 1 model equation.

(c)Using your calculated results from Part (c), sketch and numerically label the i_D versus v_DS as a function of V_GS curves. Label the Saturation, Cutoff, and Ohmic (Triode) regions.

5. Another sample quiz problem relating to FET properties. Figure from the text.

(a) If the substrate doping is N_A = 2 x 10¹⁷ cm^-3 the inverted channel charge carriers are (HOLES, ELECTRONS, BOTH HOLES AND ELECTRONS, NEUTRONS, PHOTONS) and if the substrate doping is changed to be N_D = 2 x 10¹⁷ cm^-3, the inverted channel charge carriers are (HOLES, ELECTRONS, BOTH HOLES AND ELECTRONS, NEUTRONS, PHOTONS)

(b) The input resistance looking in to the gate terminal is (CLOSE TO ZERO, GOVERNED BY R=V/I, ESSENTIALLY INFINITE) consequently the gate current I_G is (CLOSE TO ZERO, GOVERNED BY R=V/I, ESSENTIALLY INFINITE) Circle your choices.

(c) Assume t_ox = 200 Å and the substrate doping is N_A = 2 x 10¹⁷ cm^-3 Find a value for the threshold voltage, V_T from the curves.

(d) Again assume t_ox = 200 Å and W= 0.01 μm and L = 20 nm. Compute Cox and C.

This is what we use for blocking dc and passing ac in many discrete device amplifier circuits. Synonymous with coupling capacitor. Also a dc blocking capacitor is employed in your oscilloscope when switching to AC input using the soft keys. Your HANTEK DMM with allow you switch coupling by toggling the F4 button to screen 3; then F1 to yield AC volts. button. This function is the rms value of the ac waveform.

Consider the signal swing around the Q-Point which established the dynamic range of a circuit which we will use in amplifier design

Even though most of you are EE students, there is some information you can use from CS I. Of course, you can always dive deeper into CS but it messy in more ways than one, refer to the figure. I don’t know if this diagram is covered in more advanced CS courses if you decide to work on a CprE Minor. Can you tell that I am a hardware guy!