EXPERT SYSTEMS AND SOLUTIONS

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OPAMP APPLICATIONS

Session-12

PRAKASH BISWAGAR

Asst.Professor, E&C Dept.

RV College of Engg.

Bangalore

AGENDA• Recap

• Active filters

• DAC

• ADC

• Regulators

ACTIVE FILTERS

• Filters are frequency selective networks

• Used in Communications

• Can be active or passive

CLASSIFICATION OF FILTERS

FILTERS BASED ON FREQUENCY

(i) Low pass filter (LPF)

(ii) High pass filter (HPF)

(iii) Band pass filter (BPF)

(iv) Band stop filter(BSF)

(v) All pass filter

Frequency Response of filters

• Ideal

• Practical

REALIZATION OF FILTERS

1. Butterworth filters

2. Chebyshev filters

3. Elliptic filters

4. Bessel filters

BUTTERWORTH FILTERS

CHEBYSHER FILTERS

BUTTERWORTH FILTERS

• Named after the inventor “BUTTERWORTH”

• No ripple in the pass/stop band

• Have large transition width

• Filter characterized by system transfer function

• Where Pn(S) = Butterworth polynomial

• S = Complex variable = σ +jω

• Order of the polynomial indicates the order of the filter

BUTTERWORTH POLYNOMIALS

I-ORDER LPFBUTTERWORTH TYPE

• RC N/W used for filtering action

• R1 & R1’ used for gain adjustment

• OPAMP is configured in non-inverting model

D TO A CONVERTERS

Analog o/pDigital I/P

DAC

DAC SPECIFICATIONS

• Resolution

• Linearity

• Accuracy

• Settling time

• Output time

Types of DAC

1.Binary weighted DAC

2.R-2R ladder type DAC

BINARY WEIGHTED DAC

LIMITATIONS OF BINARY WEIGHTED RESISTORS

(1) As the resolution increases, the resistor value increases

(2) The accuracy is low, since depends on resistor values.

R-2R LADDER TYPE DAC

R-2R LADDER TYPE DAC

• Uses only two values of resistors

• Overcomes the limitations of Binary weighted DAC

• OPAMP is connected in inverting mode

• Each digital input is applied through R-2R network and VRef

ERRORS IN DAC

1.Linearity error

2.Offset error

3.Gain error

ADC’s• Converts analog signal into digital data• Used in Data acquisition systems & Digital

instruments etc

TYPES OF ADC

1.Counter type ADC

2.Successive approximation ADC

3.Flash or parallel converter type ADC

4.Integrated type ADC’s

(Single slope & dual slope)

COUNTER TYPE ADC

COUNTER TYPE ADC

• Initially the counter is cleared• The analog signal is applied to one of the

inputs of the comparator• Counter o/p is converted into analog, by the

DAC• The DAC O/P is compared with the incoming

signal• Conversion stops when digital O/P >Incoming

signal

SUCCESSIVE APPROXIMATIONADC

SAR ADC

• Widely used

• Similar to Counter type ADC except that ,a SAR is used

• SAR acts as programmable Up/Down counter

• Completion of conversion , triggered by a change in the state of the comparator

• Much faster than the counter type

FLASH ADC

FLASH ADC• For n-bit digital word, 2n-1 comparators are

required

• The analog sample is simultaneously applied to one input of all the comparators

• Other input to the comparator is a DC voltage derived from the pot. divider N/W

QUANTIZATION ERRORS

REGULATORS

Block diagram of a RPS

CLASSIFICATION OFREGULATORS

BASIC REGULATOR

MAIN PARTS OF A MONOLITHIC REGULATOR

• Reference voltage circuit

• Error Amplifier

• Series pass element

PRACTICAL REGULATOR

3-TERMINAL REGULATORS(FIXED O/P)

3-TERMINAL REGULATORS(SDJUSTABLE O/P)

3-TERMINAL REGULATOR(ADJUSTABLE)

DESIGN OF V.R.USING 78XX