UNIVERSITY OF OSLO
Faculty of mathematics and natural sciences
Examination in
Inf 3410 — Analog Microelectronics
Day of examination: 17. December, 2010
Examination hours:
14.30 – 18.30
This problem set consists of 3 pages.
Appendices:
none
Permitted aids:
All printed and written including calculator
Please make sure that your copy of the problem set is
complete before you attempt to answer anything.
For all questions clearly state you assumptions. You may assume all
transistors to have similar electrical properties.
All questions are weighted with an explicitly marked percentage.
Problem 1
(5%)
An important design element of integrated amplifiers is a current mirror.
Draw the schematics of such a mirror and explain functional properties and
potential errors introduced by the circuit.
Problem 2
Iout
Iin1
M1
M4
M2
Iin2
M3
Figure 1: Current-mode circuit.
The circuit shown in Figure 1 is modulating the output current as a
function of the input currents. We will assume all current (inputs and
outputs) are biased with a voltage close to the upper rail voltage. Explain
the behavior of the circuit for the following input conditions:
(Continued on page 2.)
Examination in Inf 3410, 17. December, 2010
2a
Page 2
(5%)
Iin1 = Iin2
2b
(10%)
Iin1 < Iin2
2c
(10%)
Iin1 > Iin2
Problem 3
(20%)
The transistors M2 and M4 in the circuit of Figure 1 are operating in different
regions depending on the input currents. For each of the conditions listed
in problem 2, Explain operation mode of M2 and M4 . Draw an equivalent
circuit for case b) and c).
Problem 4
VDD
M5
1
:
B2
M6
Ib
Iin
M1
M2
1 : B1
M3
Vout
M4
Ib
M7
1
:
B2
M8
VSS
Figure 2: Current-mode circuit.
In Figure 2 a simple amplifier is shown. An important feature of this
amplifier is the transistor scaling indicated by the ratios 1 : B1 and 1 : B2 .
(Continued on page 3.)
Examination in Inf 3410, 17. December, 2010
4a
Page 3
(10%)
Explain the behavior of the circuit.
4b
(5%)
What are these kinds of amplifiers called (type)?
4c
(10%)
Analyze the circuit and determine the low frequency gain.
4d
(10%)
Explain the function of the transistor scaling ratios B1 and B2 and explain
how they should be used for proper circuit performance.
4e
(10%)
Assume a load capacitor, CL , is added on the output.
bandwidth of the circuit.
4f
Estimate the
(5%)
Explain why we are unable to determine the Gain-Bandwidth (GBW) of
these kind of amplifiers.