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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
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