（free）乔治亚理工博士论文：《短沟道CMOS运放设计》

semico_ljj

1. Study of the feasibility of developing scalable op amps with all small
channel length devices
The primary aim of the research was to develop scalable op amps,
whose performance can be kept constant independent of technology as
well as channel length of the devices. It was found that small channel
lengths degrade overall circuit performance, and it is not recommended to
use all small channel length devices. Moreover, while using minimum
channel length devices, complete scalability of the op amps could not be
achieved. If the performance specifications can be expressed as ratios
(which can be made constant across different technologies), better
scalability can be achieved by increasing the channel lengths from
minimum feature size.

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2. Boost in the small-signal gain of a differential output stage using a
negative resistance circuit
Gain stages with small channel devices have poor gain, primarily
caused by large channel length modulation effects associated with the
MOS devices. A negative resistance circuit can be used to generate smallsignal
negative resistance based on the drain-to-source resistances of the
MOS devices. This negative resistance can be used to cancel the positive
drain-to-source resistances of the devices in the differential-in,
differential-out gain stages and boost the overall output resistance of the
gain stage. The extent of cancellation of the negative and positive
resistances can be made controllable based on the bias currents.

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3. Constant unity-gain bandwidth and phase margin of the op amp
When using a simple Miller compensation scheme, the unity-gain
bandwidth of the op amp depends on the transconductance of the input
devices and the compensation capacitor. The transconductance of the input
NMOS devices of the differential input pair can be designed to depend on
a resistor and ratio of device widths, which can be made independent of
the technology. Further, the phase margin can be expressed as a ratio of
NMOS transconductances, which can be kept constant across different
technologies without changing any component in the circuit.

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4. Current feedback, m g boosted source followers
The output of the op amps can be buffered using source followers,
whose effective transconductance can be boosted using current feedback.
Comparing with the simple source followers, the current-feedback source
followers can achieve larger gain as well as bandwidth for less input
capacitance, overall area, and power. They are mainly suited for driving
small loads (like, 50
) with small-signal inputs, because they have poor
distortion performance for large-signal inputs.

semico_ljj

Special！

fanjx

看看看看，应该不错的样子

fanjx

不错不错很不错

imyp

thanks for share

semico_ljj

很好，很不错！

denap

Thanks for sharing!!