mechanics of materials - university of pittsburghqiw4/academic/mems1082/chapter3-2...
TRANSCRIPT
![Page 1: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/1.jpg)
Department of Mechanical Engineering
MEMS1082
Chapter 3-2 Semiconductor devices Transistors and Amplifiers JFET
![Page 2: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/2.jpg)
Department of Mechanical Engineering
Transistors
base
Emitter
Collector
![Page 3: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/3.jpg)
Department of Mechanical Engineering
JFET Transistor
General property of a linear amplifier
i
oV V
VA =
i
oi I
IA =
IVii
oo
i
oP AA
IVIV
PPA ===
Input impedance Zi
Output impedance Zo
![Page 4: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/4.jpg)
Department of Mechanical Engineering
JFET Transistor Junction field-effect transistor Physical construction Device symbol
![Page 5: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/5.jpg)
Department of Mechanical Engineering
JFET Transistor Terminal Properties of a JFET
Transconductance amplifier: The output current is controlled by an input voltage in JFET
![Page 6: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/6.jpg)
Department of Mechanical Engineering
JFET Transistor Recall depletion region of a diode
![Page 7: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/7.jpg)
Department of Mechanical Engineering
JFET Transistor Pinch off in JFET as VDS increases
![Page 8: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/8.jpg)
Department of Mechanical Engineering
JFET Transistor The Terminal characteristics of A n-channel JFET
![Page 9: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/9.jpg)
Department of Mechanical Engineering
Junction Field Effect Transistor (FET)
The terminal characteristics of a p-channel JFET
Active region
![Page 10: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/10.jpg)
Department of Mechanical Engineering
JFET Transistor and Amplifier A simple JFET amplifier: Circuit diagram
![Page 11: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/11.jpg)
Department of Mechanical Engineering
Signal wave form and the load line
Load line
s
DSDSV V
VVA
2min,max, −
=
![Page 12: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/12.jpg)
Department of Mechanical Engineering
JFET Amplifier Distortion caused by
large input signals
![Page 13: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/13.jpg)
Department of Mechanical Engineering
dc analysis of a typical JFE amplifier
Operating point
![Page 14: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/14.jpg)
Department of Mechanical Engineering
Théveninequivalent circuit
dc analysis of a typical JFE amplifier
![Page 15: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/15.jpg)
Department of Mechanical Engineering
dc analysis of a typical JFE amplifier Rs tends to stabilize
against the variations in JFET parameters
![Page 16: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/16.jpg)
Department of Mechanical Engineering
JFET Amplifier DC and small AC analysis
![Page 17: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/17.jpg)
Department of Mechanical Engineering
JFET Amplifier DC and small AC analysis
![Page 18: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/18.jpg)
Department of Mechanical Engineering
JFET Amplifier Small AC analysis
![Page 19: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/19.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 20: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/20.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 21: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/21.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 22: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/22.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 23: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/23.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 24: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/24.jpg)
Department of Mechanical Engineering
Small signal analysis of the common-source JFET Amplifier
JFET Amplifier
![Page 25: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/25.jpg)
Department of Mechanical Engineering
For ac analysis, set dc sources to zero and replace the capacitors with a short circuit (approximation)
JFET Amplifier
![Page 26: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/26.jpg)
Department of Mechanical Engineering
Further simplified to
JFET Amplifier
![Page 27: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/27.jpg)
Department of Mechanical Engineering
Small signal analysis
JFET Amplifier
![Page 28: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/28.jpg)
Department of Mechanical Engineering
Example
![Page 29: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/29.jpg)
Department of Mechanical Engineering
Simplified small-signal equivalent circuit of a JFET
![Page 30: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/30.jpg)
Department of Mechanical Engineering
Effect of the bypass capacitor Cs If no bypass
capacitor Cs, the simplified JFET amplifier circuit will be
![Page 31: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/31.jpg)
Department of Mechanical Engineering
Effect of the bypass capacitor Cs Effect of the bypass capacitor Cs
0=∆ GSv
![Page 32: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/32.jpg)
Department of Mechanical Engineering
Example: JFET amplifier with Cs removed
( )097.0
1−=
+−=
fss
LDfsV yR
RRyA
Ω== kRZ Gi 100
7.9−==L
iVi R
ZAA
Ω== kRZ Do 1
![Page 33: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/33.jpg)
Department of Mechanical Engineering
Frequency response of the JFET Amplifier
![Page 34: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/34.jpg)
Department of Mechanical Engineering
Frequency response of the JFET Amplifier
Gate-source and gate-drain pn junctions are reverse biased.The depletion layers are a separation of mobile charge carriers, thus at high f, we have CGD and CGS
CDS is caused by other less predominant factors, such as stray capacitance
For 2N3819 JFETCGD =CGS=4pF, CDS=0
![Page 35: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/35.jpg)
Department of Mechanical Engineering
Frequency response of the JFET Amplifier
GSi vv ∆=∆Note:
Convert the controlled current source to controlled voltage source:
![Page 36: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/36.jpg)
Department of Mechanical Engineering
Frequency response of the JFET Amplifier
KVL about the right loop
GSi vv ∆=∆Note:
![Page 37: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/37.jpg)
Department of Mechanical Engineering
Frequency response of the JFET Amplifier
Equivalent circuit
![Page 38: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/38.jpg)
Department of Mechanical Engineering
Example: High frequency JFET amplifier
![Page 39: Mechanics of Materials - University of Pittsburghqiw4/Academic/MEMS1082/Chapter3-2 transistors-JFET.pdf · Gate-source and gate -drain pn junctions are reverse biased. The depletion](https://reader030.vdocument.in/reader030/viewer/2022040802/5e3ad2971e34bf38876a0702/html5/thumbnails/39.jpg)
Department of Mechanical Engineering
Example: High frequency JFET amplifier