Question 2. Common-Source with Resistive Load
When dealing with weak signals, such as microphone amplifiers or signal conditioning circuits for other sensing devices, common-source
MOSFET amplifiers are often used as the first stage of amplification because of the high voltage gain they can provide.
In his final task, Peilin must optimize a common-source amplifier with a resistive load. Assume λ = 0 and γ
= 0. For VDD = 5V , Vin = 0.9 V + small signal, RD = 15kΩ and Ldrawn = 2µm, find out the
value Wdrawn to obtain a voltage gain |Av | > 10 and VOUT (the DC biasing voltage at the output) close to 2.5V as much as possible.
VTO : threshold voltage with zero VSB ( unit : V )
GAMMA : body effect coefficient ( unit : V 1/2 )
PHI : 2ΦF ( unit : V )
TOX : gate oxide thickness ( unit : m )
NSUB : substrate doping ( unit : cm−3 )
LD : source/drain side diffusion ( unit : m )
UO : channel mobility ( unit : cm2 /V/s )
LAMBDA : channel-length modulation coefficient ( unit : V −1 )
CJ : source/drain bottom-plate junction capacitance per unit area ( unit : F/m2 )
CJSW : source/drain sidewall junction capacitance per unit length ( unit : F/m )
PB : source / drain junction built-in potential ( unit : V )
MJ : exponent in CJ equation ( unitless )
MJSW : exponent in CJSW equation ( unitless )
CGDO: gate-drain overlap capacitance per unit width ( unit : F/m )
CGSO : gate-source overlap capacitance per unit width ( unit : F/m )
JS : source/drain leakage current per unit area ( unit A/m2 )
Vacuum permittivity (ϵo ) = 8.85×10−12 (F/m)
Silicon oxide dielectric constant (ϵr ) = 3.9
After days of intense focus, Peilin finally submitted his solutions for the small-signal MOS- FET models and the common-source amplifier.
He had met all the challenges Xuyang had thrown at him, from understanding MOSFET biasing in Homework 5 to mastering the in- tricacie
small-signal analysis and amplifier optimization in Homework 6.
In
a
brief
yet
significant
meeting,
Xuyang
reviewed
Peilin’s
work.
“Excellent
job, Peilin,” Xuyang said with a nod of approval. “Your understanding of MOSFET technology is im- pressive, and your solutions demonst
Peilin felt a surge of pride. He had not only completed the tasks but had also deepened his understanding of crucial electronic concepts.
More importantly, he had proven his value to Blue Tiger Electronics.
As Peilin left Xuyang’s office, he looked forward to the new challenges ahead. With a renewed sense of confidence, he knew he was
ready to tackle whatever came next in his journey as an engineer at Blue Tiger Electronics.