Operational-Amplifier andData-Converter Circuits

Outline

•The Two-Stage CMOS Op Amp•The Folded-Cascode CMOS Op Amp•The 741 Op-Amp Circuit•DC Analysis of the 741•Small-Signal Analysis of the 741•Gain, Frequency Response, and Slew Rate of

the 741•Data Converters- An Introduction•D/A Converter Circuits•A/D Converter Circuits

Sampling of Analog SignalsSample-and-hold (S/H)

A/D and D/A Functional Blocks

Sample-and-hold

After Filtering

Outline

•The Two-Stage CMOS Op Amp•The Folded-Cascode CMOS Op Amp•The 741 Op-Amp Circuit•DC Analysis of the 741•Small-Signal Analysis of the 741•Gain, Frequency Response, and Slew Rate of

the 741•Data Converters- An Introduction•D/A Converter Circuits•A/D Converter Circuits

Binary-Weighted Resistors

NNbbb

D222 2

211

bN: least significant bit (LSB)b1: most significant bit (MSB)

io =

vo = The spread between resistances is large!!

R-2R ladder !!

R-2R Ladders

io =

How to actually generate these currents? Current Sources

Practical Circuit Implementation

VN =

VN-1 =

How to make the switches?

Current Switches Implementation

How to eliminate the base current? MOSFET !!

Outline

•The Two-Stage CMOS Op Amp•The Folded-Cascode CMOS Op Amp•The 741 Op-Amp Circuit•DC Analysis of the 741•Small-Signal Analysis of the 741•Gain, Frequency Response, and Slew Rate of

the 741•Data Converters- An Introduction•D/A Converter Circuits•A/D Converter Circuits

Feedback-Type Converter

Slow if the converter starts from zeroTrack incremental changes in the input rapidly

Dual-Slope A/D Converter

Dual-Slope A/D Converter (con’t)

Slow ConversionHigh AccuracyIndependent of exact values of R and C

Parallel or Flash Converter

Rather complex circuit implementationFast –Can be complete within one clock cycle

Charge-Redistribution Converter

Sample Phase

Charge-Redistribution Converter

Hold Phase

Charge-Redistribution Converter

Charge-Redistribution Phase

Reasonable accurate conversionModerate speed