SIGNAL PROCESSING WITH ANALOG CIRCUIT

Chun Lo

Analog circuit design Main disadvantage: low precision

Due to mismatch in analog circuit components such as transistors, resistors and capacitors

e.g. Amplifiers: lower input signal dynamic range Comparator: lower signal resolution

Transistors: lower accuracy in current mode DAC Advantage:

Less power consumption Possibly smaller area

Mismatch correction By trimming device

Larger device, layout technique in component mismatch

Autozeroing, correlated double sampling in amplifiers

Cost of extra area, power and design complexity

By in herent programming elements Floating gate MOSFETs

First paper Floating Gates Transistors For Precision

Analog circuit Design: An Overview Srinivasan, Graham and Hasler

Second paper Analog Floating –Gate On chip Auditory

Sensing System Interfaces Hasler, Smith, Graham, Ellis and Anderson

First paper Structure of Floating Gate MOSFET

Programming floating gate transistors Programming precision Charge retention

Application examples of Floating Gate MOSFET Differential pairs DAC ADC

MOSFET MOS Transistor Floating Gate MOSFET

The gate is completely surrounded by SiO2 No DC to ground Used in Flash memory, ROM

Programming FG-MOSFET Setting the DC voltage Add or remove charge Mainly two methods

Fowler Nordheim tunneling As a global eraser for all floating gates

Hot electron injection Program each floating gate to the desired value

individually

Programming precision What is the smallest drain current change

A single electron change results in an accuracy of or 12 bits

exp( )exp( )g so

T T

V VI I

U U

( )exp( )exp( )g g s

oT T

V V VI I IU U

exp( ) 1g

T

VII U

T

QVC

exp( ) 1T T

I QI U C

42.8 10X

Charge Retention Short term drift

Observed immediately after programming Proportional to the amount of change that

is programmed into the floating gate Long term charge loss

Themionic emission Related to both temperature and time

Applications Differential pair DAC ADC

Second paper Advance in analog VLSI circuits

Performance close to DSP More option for designeer

Analog Digital Partition Signal Processing Circuits Noise Suppression for speech

enhancement Speech Recognition

Analog Digital Partitioning Power and space

No overhead for tuning and programming Work in subthreshold save power

SN VS Cost

Analog Signal Processing

Noise suppression Main Idea: Attenuate the noise

components

Speech Recognition HMMs

States, transition probabilities and Hidden states are words, output is audio

signal produced by speaker Recognition problem: what is the state of

the system