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EE 310 Electronic Circuit Design 1
Experiment 5
Active Biasing of the MOSFET Amplifier
By: Michael J. Stachnik
Introduction:
The purpose of this lab is extremely simple, build a current source and understand why
Integrated Circuit (IC) designers use them. The type of current source that will be constructed in
this experiment is called a Current Mirror. A Current Mirror is a circuit designed to copy a
current through one active device by controlling the current in another active device of a circuit,
keeping the output current constant regardless of loading. A Current Mirror can be designed
from bipolar junction transistors (BJT) or field-effect transistors (FET), which are extremely
useful in biasing other transistors to carry out a number of analog circuit functions. Hopefully
this lab will reinforce the MOSFET analysis being taught in class as well as answer a few
questions on what exactly current sources are and how they can be constructed.
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TASK A:
A1. Calculate RREF
iD = Kn * (VGS - VTN)2
100 μA = 201 μA * (VGS – 0.623 V)2
VGS = -0.082 V or 1.32 V
IREF = (V+ - VGS - V-) / RREF
100 μA = (10 V – 1.32 V – 0 V) / RREF
RREF = 86.7 kΩ
A2. Measure IREF
Using a 86.5 kΩ resistor and the steps supplied in Section 3. Experimental Effort parts 1
through 3, we were able to measure:
IREF = 98.56 μA
A3. Measure IO
By setting VDS2 = VDS1 = VGS and following the steps supplied in Section 3.
Experimental Effort parts 1 through 3, we were able to measure:
IO = 99.67 μA
A4. Derive the effect of Kn on IO / IREF
IO = [(Kn2 * IREF) * (1 + λn * VDS2)] / [Kn1 * (1 + λn * VGS)]
IO = (Kn2 / Kn1) * IREF
IO ≈ IREF
A5. Measure IO for two different VDS2 values
Set VDS2 IO
1 1.32 V 99.67 μA
2 4.0 V 102. 05 μA
EE 310 Electronic Circuit Design 1
Experiment 5
Active Biasing of the MOSFET Amplifier
By: Michael J. Stachnik
Introduction:
The purpose of this lab is extremely simple, build a current source and understand why
Integrated Circuit (IC) designers use them. The type of current source that will be constructed in
this experiment is called a Current Mirror. A Current Mirror is a circuit designed to copy a
current through one active device by controlling the current in another active device of a circuit,
keeping the output current constant regardless of loading. A Current Mirror can be designed
from bipolar junction transistors (BJT) or field-effect transistors (FET), which are extremely
useful in biasing other transistors to carry out a number of analog circuit functions. Hopefully
this lab will reinforce the MOSFET analysis being taught in class as well as answer a few
questions on what exactly current sources are and how they can be constructed.
, Page 2
TASK A:
A1. Calculate RREF
iD = Kn * (VGS - VTN)2
100 μA = 201 μA * (VGS – 0.623 V)2
VGS = -0.082 V or 1.32 V
IREF = (V+ - VGS - V-) / RREF
100 μA = (10 V – 1.32 V – 0 V) / RREF
RREF = 86.7 kΩ
A2. Measure IREF
Using a 86.5 kΩ resistor and the steps supplied in Section 3. Experimental Effort parts 1
through 3, we were able to measure:
IREF = 98.56 μA
A3. Measure IO
By setting VDS2 = VDS1 = VGS and following the steps supplied in Section 3.
Experimental Effort parts 1 through 3, we were able to measure:
IO = 99.67 μA
A4. Derive the effect of Kn on IO / IREF
IO = [(Kn2 * IREF) * (1 + λn * VDS2)] / [Kn1 * (1 + λn * VGS)]
IO = (Kn2 / Kn1) * IREF
IO ≈ IREF
A5. Measure IO for two different VDS2 values
Set VDS2 IO
1 1.32 V 99.67 μA
2 4.0 V 102. 05 μA
