11 351 ADC, DAC, op-amps, cont, pre

11 351 ADC, DAC, op-amps, cont, pre - Back to Op Amp...

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1 1 Back to Op Amp Circuits 2 () ( ) 2 01 1 22 2 2 1 2 1 2 2 1 2 11 2 2 12 2 1 2 2 1 2 2 21 12 1 1 1 1 1 i ii i i i R EE R RR E E E E E R /RR E E R ER/R R E R R R R R R R R R −− −= =− − = + − + ⎡⎤ =+ + + ⎣⎦ ⎛ ⎞ + = ⎜⎟ ⎢⎥ ++ ⎝ ⎠ =−= 2 1 R R Example: differential amplifier 2 2 i R E E + = + E E + = R 2 R 1 2 02 1 1 R E R note the typos in Figliola & Beasley 2 i E E I == I 2 Figliola & Beasley Figure 6.20c Discussion: E o in terms of E i s? No current into/from “-” terminal I 2 Op Amp Circuits: Differential Amplifier
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2 3 Example: integrator Discussion: E o in terms of E i ? Figliola & Beasley Figure 6.20e Op Amp Circuits: Integrator 4 Comparator Without a feedback loop, the difference between E i1 and E i2 is amplified by A, the internal amplifier gain. The output voltage saturates just below the supply voltage E s . If E i2 is a known reference voltage, then the op amp can be used to decide if E i1 is < or > than E i2 . Figure from Figliola & Beasley.
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3 5 Integrating Analog and Digital Devices DAC 6 Digital-to-Analog Converter (D/A) An M-bit device that converts a digital binary word into an analog voltage. M switches that toggle between E ref and GND (shown with all switched to ground) Specifications are analog voltage range output E FSR and M. Figure adapted from Figliola & Beasley, Figure 7.6
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4 7 Digital-to-Analog Converter An M-bit device that converts a digital binary word into an analog voltage. Summing amplifier with all the V i = E ref . I R = E ref /R I 2R = E ref /2R I 2R = E ref /2 M-1 R I = I i 1 1 2 M m ref m m c IE R = = where c m = 0,1 depending on switch 0 1 1 2 M m rr e f r m m c EI R E R R = =− = = -E 0 /R r I Figure adapted from Figliola & Beasley, Figure 7.6 8 Digital-to-Analog Converter An M-bit device that converts a digital binary word into an analog voltage. 0 1 1 2 M m e f r m m c R E R R = = Figure adapted from Figliola & Beasley, Figure 7.6 Specifications for a DAC are analog voltage range output E FSR and M. Discussion If E FSR = 2.5 V and M = 8, what voltage is the LSB?
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5 9 Digital-to-Analog Converter An M-bit device that converts a digital binary word into an analog voltage. Figure adapted from Figliola & Beasley, Figure 7.6 Discussion If E FSR = 2.5 V and M = 8, what voltage is the LSB?
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This note was uploaded on 11/28/2010 for the course ENES enes100 taught by Professor Staff during the Spring '10 term at Maryland.

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11 351 ADC, DAC, op-amps, cont, pre - Back to Op Amp...

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