Download Assign. 3 File

FAKULTI KEJURUTERAAN ELEKTRIK
UNIVERSITI TEKNOLOGI MALAYSIA
SKEL 4283
Assignment 3
Use TSMC 0.25 µm process parameters in all your calculations.
Design a differential amplifier with resistive load with the following design
specifications: (you cannot design a circuit exactly the same with your course
mate)
VDD
RD
RD
Vo1
Vo2
M6
R1
R2
M7
Vi1
Vi2
ISS
1.
Oct. 2016
M4
M5
M2
M3
M1
(i) All transistors are in saturation.
(ii) L = 2 μm for all transistors.
(iii) Differential voltage gain |AVD,diff| = |(vo1 – vo2)/(vi1 – vi2)| must be at least 5.
(iv) ISS ≤ 150 μA.
You may ignore body effect.
(a) Show all your calculations. Summarize your design in Table 1.
Table 1: Diff-amp design values
ISS
W1, W2, W3, W5
W4
R1
R2
W6, W7
|AVD,diff|
RD
(b) Determine a value of Vin,CM (DC voltage at gate of M6 and M7) that ensures
the circuit works as an amplifier. This value must be high enough to ensure
current source can operate and low enough to ensure M6 and M7 are
saturated. With your chosen Vin,CM, perform a simulation to obtain operating
point information of your circuit. Use .op SPICE command. Attach the .op
result in your report. From the simulation result, prove that M1, M2, M6, and
M7 are saturated.
(c) Measure the gain using transient analysis. The SPICE code for transient
analysis is:
* assuming your common VIN is 1.3 V
* define sine wave input: DC level of 1.3 V
* 5 mV peak (i.e. 10 mV p-p), 1 kHz frequency
vi6 g6 0 sine(1.3 5m 1k) * assuming VIN1 = 1.3 V
vi7 g7 0 sine(1.3 -5m 1k) * assuming VIN2 = 1.3 V
.tran
3u 3m
The statements above tells LTSpice that both inputs has DC voltage of 1.3 V
and a 5 mVp sinusoid with frequency of 1 KHz but out of phase with each
other. In other words, vi6 – vi7 is a 1 kHz 10 mVp (20 mVp-p) sinusoid. The
statement .tran 3u 3m instructs LTSpice to do calculations from 0 – 3
ms (3 periods of the input sinusoid) with time step of 3 µs.
Simulate the circuit. Show both plots of vi1 – vi2 input and vo1 – vo2 output
signals on the same plot pane and calculate the AVD,diff gain by measuring the
peak output signal amplitude divided by 10 mV. Specify your measured gain
and compare it to calculated value. Attach the SPICE code and the transient
simulation plot in your report.
Marking scheme:
Q1
80 marks
Table 1 not included
Result of .op simulation not attached
M1, M2, M6, M7 not proven sat.
SPICE code for transient analysis not included
Plots from transient simulation not included
Specifications not met
Similar design to another course mate
-20 marks
-10 marks
-10 marks
-10 marks
-10 marks
-10 marks
-40 marks