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 I

U U

exp( ) 1g

T

VI

I U

T

QV

C

exp( ) 1T T

I Q

I 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