Download EE 140 Midterm Exam: Electrical Engineering Amplifier and Circuit Design and more Exams Electrical Circuit Analysis in PDF only on Docsity!
C. Nguyen March 19, 2009
INSTRUCTIONS
- Read all of the instructions and all of the questions before beginning the exam.
- There are 3 problems on this midterm exam, totaling 115 points. The tentative credit for each part is given to help you allocate your time accordingly. You have a total of 1 hour and 20 minutes to finish this exam. Be careful not to spend all your time on any one part.
- This is a closed book exam, except you can have one two-sided 8.5″×11″ sheet of notes.
- Unless otherwise noted on a particular problem, you must show your work (in the space pro- vided plus the backs of the pages) for all problems to receive full credit; simply providing answers will result in only partial or no credit, even if the answers are correct. (But note that writing down a formula by inspection counts as “showing work”.) If you require extra space beyond what is provided, be sure to turn in any material that is required to support your solu- tions. Note that there are extra pages at the end of this exam. Do not use any attached pages until you have exhausted the pages contained in this exam.
- Turn in the entire exam, including this cover sheet.
- Put your name on every page of this exam, as well as on any additional material that you submit.
- Be sure to provide units where necessary.
Signature : ___________________________________________
Problem 1: / 25 points
Problem 2: / 45 points
Problem 3: / 45 points
Total: / 115 points
C. Nguyen March 19, 2009
Problem 1.
In the amplifier circuit below, VS is chosen so that I (^) C 2 = 1mA and device parameters (at this bias point) are included to the right, but you actually might not need this information for this problem. The information is given mainly so that you can make educated decisions on what to include and what to neglect when writing out your formulas.
Write expressions for:
(a) the small signal gain v (^) o / vs
(b) the 3dB cut-off frequency f (^) H based on open-circuit time constant analysis
Total 25 points
C. Nguyen March 19, 2009
Problem 2.
The circuit below comprises a bias voltage generator (on the left side) for the cascode current source on the right side. The ( W / L ) ratios given are in microns, and all required device data is provided in the box below. Ignore Body effect in this problem.
(a) Find the RREF that sets I (^) REF = 50μA. Give an equation and a numerical value.
(b) If I (^) o = I (^) REF = 50μA, what is the minimum voltage that the drain of M 2 can take while keeping both M 1 and M 2 in saturation. (c) Choose n so that the M 1 - M 2 cascode allows the maximum swing for an amplifier using this current source. Give an expression and numerical value for n.
(d) Assuming I (^) REF = 50μA, provide an expression and numerical value for the output resistance Ro.
(e) Suppose n =1. What then would be the expression for output resistance Ro? (No need to cal- culate it; just give the expression.)
Device Parameters: NMOS: Vtn 0 = 0.7V, μ n Cox = 200μA/V^2 , λ n = 0.05 V- PMOS: Vtp 0 = - 0.7V, μ p Cox = 100μA/V^2 , λ p = 0.1 V-
VDD = 2V
M 1
M 2
Ro
IREF RREF
M 3
M 4
M 6 M 5
M 7
Io
20
20
20
20
20
20
݊ ൈ
20
Total 45 points
C. Nguyen March 19, 2009
Problem 2. (continued)
More work space next page.
C. Nguyen March 19, 2009
Problem 3.
This problem involves the circuit below, where the ( W / L ) ratios given are in microns, and all required device data is provided in the box below.
Ignore Body effect when determining each of the following:
(a) Equation and numerical value for the output voltage swing when R 1 = 100kΩ.
(b) Equation and numerical value for the common-mode input voltage to output voltage v (^) o gain when R 1 = 100kΩ.
(c) Equation and numerical value for the differential input voltage ( v (^) i 1 - v (^) i 2 ) to output voltage v (^) o gain, i.e., v (^) o /( v (^) i 1 - v (^) i 2 ),when R 1 = 100kΩ.
(d) Equation (only) for the output resistance Ro when R 1 = infinity.
M 2
Ro Vo
VDD = 1.5V
M 1
M 3
M 4
M 6 M 5
M 7
R 1
RS = 1kΩ
M 9^ M^8
40
40
10 0.5 10
10
10
10
10
10
VSS = -1.5V
Vi 1 Vi 2
Device Parameters: NMOS: Vtn 0 = 0.7V μ n Cox = 200μA/V^2 λ n = 0.05 V- PMOS: Vtp 0 = - 0.7V μ p Cox = 100μA/V^2 λ p = 0.1 V-
IREF =20μA
Total 45 points
C. Nguyen March 19, 2009
Problem 3. (continued)
More work space next page.
C. Nguyen March 19, 2009
Extra Page.
