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(ELEC202)[2008](f)midterm~ee_lkmah^_10287.pdf
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Name: Solution ID No.


Chinese Name:

1
4


2
10


3
26


Total
40





The following equations may be useful:
Id = Is(

kn = nCox
kn' = nCox
For Vds < Vgs C Vtn Id = nCox
[(Vgs C Vtn)Vds C
Vds2]
For Vds > Vgs C Vtn Id =
nCox
(Vgs C Vtn) 2(1 + nVds)
For ax2 + bx + c = 0 x1,2 =



(1a) A diode D1 is driven by a current source Iin as shown in Fig. 1. 2 marks
When Iin = 1mA, Vd = 0.7V. What is Vd when Iin = 200A?
You may assume that the thermal voltage is VT = 26mV.







V





Fig. 1








(1b) When the temperature is 27oC (300K), the thermal voltage is VT = 26mV. 2 marks
What is Vd when Iin = 1mA and the temperature is 77oC (350K)?




















(2a) For a particular process, nCox = 32A/V2 and Vtn = 0.75V. Compute 2 marks
the current Id passing through an NMOS transistor M1 with (W/L)1 = 4/1
when Vgs1 = 1V. Assume M1 works in the active region.










(2b) In addition to nCox and Vtn, we also learn that n = 0.1/V. What is the 2 marks
output resistance of M1?










(2c) With the given nCox, Vtn and n, Compute the current passing through 2 marks
M1 when Vgs1 = 1V and Vds1 = 1V.










(2d) For the transistor in (2c), compute the current passing through M1 when 1 mark
Vgs1 = 1V and Vds1 = 5V.












(2e) Using the results of (2c) and (2d), compute the output resistance of M1. 1 mark










(2f) What is the maximum gain of M1? 2 marks









(3a) Fig. 2 shows an inverting amplifier with a resistive load. Determine the 8 marks
maximum current that the resistor could provide to the transistor, and
sketch a few I-V characteristics of M1 with 0.1V increment of Vin.
Sketch also the load line of the resistor on the same figure.
Process parameters: nCox(W/L)1 = 500A/V2, Vtn = 0.9V, n = 0.1/V.





Fig. 2






























(3b) From the I-V curves and the load line of (3a), sketch the voltage transfer 2 marks
characteristic (VTC) of the inverting amplifier, that is, Vo vs Vin.
























(3c) For Vo = 1V to Vo = 4V, compute the gain of the amplifier using the 2 marks
graph of (3b).







(3d) Draw the small signal model of the amplifier, and compute the gain. 4 marks
Provide the numerical answer at Vin = 1.2V.



gvR


(3e) The inverting amplifier of (3a) is replaced by an active load as shown 2 marks
in Fig. 3. Compute the bias resistor Rb if the current source has a bias
current Ib of 22.5A.
PMO