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UNIVERSITY OF CALIFORNIA College of Engineering Department of Electrical Engineering and Computer Sciences
Professor Oldham Spring 1999
EECS105 — Midterm 2
Thursday, 8 April 1999
Your name: ______________ ____________________
Your discussion TA: r Allan Chang r Lily Tam
- This is a closed book exam, but you may use your 2 pages of notes. - Please do all your work on the pages of this exam. Ask if you need extra paper. - Full credit will be given only when you indicate the source of your answer, such as a table, graph, or calcula- tion. - Please write your name in the above space - SPECIAL NOTES: 1. QUESTIONS: Because it is disturbing to others in the exam when we pass by to answer questions, we must ask you to please limit your questions. Re-read the exam question and be sure that the data or equation you need is not already provided. 2. GRAPHS AND FORMULAS PROVIDED: At the back of the exam are several pages of formulas, and data in the form of graphs. Please look for information here rather than asking a question. 3. SOME PARTS OF THE EXAM ARE GRADED WITH NO PARTIAL CREDIT. They are noted. You may wish to double check your answers on those parts. 4. DEVICE PROPERTIES: Unless otherwise specified, assume n-channel transistors have , and p-channel transistors have. In small-signal calculations assume a lambda of 0.05 for both types. Assume bipolar transistors have beta of 100 and of 10-15 A (both npn and pnp transistors). In small-signal calculations assume the Early volt- age is 20 V. You are to ignore lambda and Early voltage in biasing calculations. SCORE Problem 1 (15 pts.) Problem 2 (15 pts.) Problem 3 (20 pts.) Problem 4 (25 pts.) Problem 5 (25 pts.) TOTAL (100 pts.)
first last
Yes, I have looked these over. (Check box)
Vtn = 0.5 V , μCox = 50 μA/V 2 Vtp = – 0.5V , μCox = 25 μA/V^2
IES
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Problem 1 (15 pts., NO Partial Credit)
You buy three voltage amplifiers with the following specifications:. You hook
them up in series (i.e., output 1 = input 2, etc.), and place them in a black box. You are going to sell this box as a transconductance amplifier. What are the specifications of the transconductance amplifier?
Problem 2 (15 points)
a. Find the phasor representing the ratio of short-circuit output current to input current for the following circuit:
b. What is the general shape of the frequency response? Sketch magnitude vs frequency on dB scale provided on pg. 2.
Rin = 10 5 , Rout = 10 5 , A = 10
A 1 A 2 A 3
transconductance amplifier
Gm = _____________
Rin = _____________ Rout = _____________
−
v 2
i 1
iIN R 1 C g^2 V^2 2
βi 1 R iOUT L
R 2
A 1
I out ≡ ------- I in- =___________________________________________
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Problem 3 (20 points)
Sketch the Bode plot on the graphs provided for the following function. Please show your work. (Neatness and clarity are important.) Only straight-line approximations are wanted.
F
200 jω 1 jω 200
× +---------
= ( --------------------------------------------------------------------------------------- 2 +jω) ( 1 + 100 jω) ( 1 +0.0002jω)-
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Problem 3 Worksheet
6 of 8
Problem 4 Worksheet
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Problem 5 (25 points)
a) You are given one “power nMOS” transistor and need to construct a transistor circuit to drive an 8 ohm
speaker through a coupling capacitor. (The “power nMOS” transistor has a 1V threshold, a of , and. The source is connected to the body internally.) Your circuit should have a voltage gain of about 0.5 at higher frequencies (that is, at frequencies high enough that the impedance of is negli- gible). (Note that must be quite large to have a good low frequency response.) The bias current source you have available is essentially ideal (i.e., infinite parallel resistance). You choose the circuit below.
a) Draw the small-signal model for this amplifier in the box opposite, ignoring all internal device capacitances and parasitic resistances.
b) Solve for the “mid-band” gain (formula in terms of circuit and device parameters). The mid-band gain is
a real quantity. It is the gain at frequencies high enough that coupling capacitors act as shorts, yet the fre- quency is low enough that capacitors to ground are negligible.
c) Find the mid-band gain of the circuit at a bias current of.
C X W ⁄ L 104
μCox = 50 μA/V^2 C (^) X C (^) X
8 Ω speaker
V (^) DD (^) C X I BIAS
R (^) S
−
v (^) S
100 KΩ
A M
A M = ____________
A (^) M I BIAS =10 mA
A M =____________
A.
Appendix A:
A.
Appendix B:
A.
(EQ 6.10)
(EQ 6.22)
(EQ 6.30)
(EQ 6.31)
(EQ 6.48)
Appendix D: Values
Appendix E: SIA unit multipliers:
φB V (^) thln
p (^) po p (^) no -------^ and^ φB^ V^ thln^
n (^) no n (^) po
p (^) n ( x (^) n) = p (^) no ⋅ e V^ D^ ⁄^ V^ th and n (^) p ( – x (^) p) = n (^) po e V^ D^ ⁄V^ th
J qn (^) i^2
D (^) p N (^) d W (^) n
D (^) n N (^) a W (^) p
= + --------------^ (e V^ D^ ⁄^ V^ th– 1 )
I (^) D qn (^) i^2 A
D (^) p N (^) d W (^) n
D (^) n N (^) a W (^) p
= (^) + --------------^ ( e V^ D^ ⁄^ V^ th– 1 ) =I (^) o ( e V^ D^ ⁄^ V^ th– 1 )
C (^) j
C (^) jo 1 – V (^) D ⁄φB
q =1.6 × 10 –^19 C
V (^) t = kT ⁄ q = 0.026 V
ε 0 = 8.85 × 10 –^14 F ⁄cm
εoxide = 3.9ε 0
εSi = 11.7ε 0
M = 10 6
K = 10 3
m = 10 –^3
μ = 10 –^6
n = 10 –^9
p = 10 –^12
f = 10 –^15
