Lect2UP340_(100501)

Lect2UP340_(100501) - Lecture 340 Characterization of DACs...

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Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-1 CMOS Analog Circuit Design © P.E. Allen - 2010 LECTURE 340 – CHARACTERIZATION OF DACS AND CURRENT SCALING DACS LECTURE ORGANIZATION Outline • Introduction • Static characterization of DACs • Dynamic characterization of DACs • Testing of DACs • Current scaling DACs • Summary CMOS Analog Circuit Design, 2 nd Edition Reference Pages 613-626 Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-2 CMOS Analog Circuit Design © P.E. Allen - 2010 INTRODUCTION Importance of Data Converters in Signal Processing PRE-PROCESSING (Filtering and analog to digital conversion) DIGITAL PROCESSOR (Microprocessor) POST-PROCESSING (Digital to analog conversion and filtering) ANALOG SIGNAL (Speech, sensors, radar, etc.) ANALOG OUTPUT SIGNAL CONTROL ANALOG A/D D/A DIGITAL ANALOG
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Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-3 CMOS Analog Circuit Design © P.E. Allen - 2010 Digital-Analog Converters Digital Signal Processing System Microprocessors Compact disks Read only memory Random access memory Digital transmission Disk outputs Digital sensors DIGITAL- ANALOG CONVERTER Filter Amplifier Analog Output Reference Fig. 10.1-01 Characteristics: • Can be asynchronous or synchronous • Primary active element is the op amp • Conversion time can vary from fast (one clock period, T ) to slow (2 No. of bits * T ) Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-4 CMOS Analog Circuit Design © P.E. Allen - 2010 Analog-Digital Converters 060922-01 Analog Input Sample and Hold Digital Signal Processing System Microprocessors Compact disks Read only memory Random access memory Digital transmission Disk outputs Digital sensors ANALOG- DIGITAL CONVERTER Reference Characteristics: • Can only be synchronous (the analog signal must be sampled and held during conversion) • Primary active element is the comparator • Conversion time can vary from fast (one clock period, T ) to slow (2 No. of bits * T )
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Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-5 CMOS Analog Circuit Design © P.E. Allen - 2010 STATIC CHARACTERISTICS OF DIGITAL-ANALOG CONVERTERS Block Diagram of a Digital-Analog Converter V REF DV REF v OUT = KDV REF Output Amplifier Scaling Network Voltage Reference Binary Switches b 0 b 1 b 2 b N -1 Figure 10.1-3 b 0 is the most significant bit (MSB) The MSB is the bit that has the most (largest) influence on the analog output b N -1 is the least significant bit (LSB) The LSB is the bit that has the least (smallest) influence on the analog output Lecture 340 – Characterization of DACs and Current Scaling DACs (5/1/10) Page 340-6 CMOS Analog Circuit Design © P.E. Allen - 2010 Input-Output Characteristics Ideal input-output characteristics of a 3-bit DAC 1.000 0.875 0.750 0.625 0.500 0.375 0.250 0.125 0.000 Analog Output Value Normalized to V REF 000 001 010 011 100 101 110 111 Digital Input Code Vertical Shifted Characteristic Infinite Resolution Characteristic 1 LSB Fig. 10.1-4
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Lect2UP340_(100501) - Lecture 340 Characterization of DACs...

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