MODULE V
MODULE V INTEGRATED CIRCUITS
(pg 5 same points in paragraph form is given)
1. ANALOG AND DIGITAL DATA CONVERSION
Importance of signal measurement and analysis to determine characteristics of signals.
Analysis begins with signal acquisition.
Sampling: Most common method for acquiring signals, involves capturing values at discrete times.
2. Signal Definitions
2.1. Analog Signal
Defined over a continuous time interval; amplitude can take a continuous range of values.
2.2. Quantisation
Quantisation: Representation of a variable by a finite set of discrete values.
Quantised Variable: Can assume only finite distinct values.
2.3. Discrete Time Signal
Defined only at certain points of time, making the independent time variable quantised.
Sampled-Data Signal: Results from sampling an analog signal at discrete intervals.
2.4. Digital Signal
Both time and amplitude are quantised.
Represented by a sequence of words containing finitely many bits.
3. D/A & A/D Converters
3.1. D/A Converter (DAC)
Converts digital data to equivalent analog data, used to drive motors and analog devices.
3.2. A/D Converter (ADC)
Converts analog data into equivalent digital data (binary format).
Both converters available as monolithic integrated circuits.
4. SPECIFICATIONS OF D/A CONVERTER
4.1. Accuracy
Components may experience drift, ageing, noise, leading to performance degradation.
Absolute Accuracy: Maximum deviation of output from ideal value expressed in fractions of 1 LSB.
Errors classified into static (offset and gain errors) and dynamic errors.
4.2. Offset Voltage
Output should ideally be 0V when all bits are 0, but a small output voltage (offset voltage) is present.
Offset error can be adjusted to ensure the output goes through the origin.
4.3. Linearity
Full-scale Error: Max deviation of output from expected value, expressed as a percentage of full scale.
Linearity Error: Max deviation in step size from ideal; ideal D/A shows equal increments in output for equal increments in input.
4.4. Differential Nonlinearity Error (DNL)
DNL measures the difference between the ideal output response and actual for successive D/A codes.
Ideal response has output values exactly one code apart.
4.5. Integral Nonlinearity Error (INL)
INL reflects deviation of an actual transfer function from a straight line after adjusting for offset/gain errors.
4.6. Monotonicity
D/A converter is monotonic if output increases with binary input, no downward steps in the staircase output.
4.7. Resolution
Defined as the smallest change in analog output for a change in digital input; resolution = weight of LSB.
Percentage resolution calculated; for n-bit digital input, total number of steps is (2^n – 1).
4.8. Settling Time
Time for the D/A output to stabilize within ±(1/2) LSB of the final value.
Affected by switching times, stray capacitances, and inductances.
4.9. Temperature Sensitivity
Analog output varies with temperature; sensitivity ranges from ±50 ppm/°C to ±1.5 ppm/°C.
4.10. R2R Ladder D/A Converter
Uses resistors of only two values, simplifying design.
The output is a weighted sum of digital inputs.
5. A/D CONVERTER
5.1. Conversion Process
Converts analog signal into n-bit binary coded digital output.
Samples analog input at a frequency higher than the maximum input signal component.
5.2. Components and Functioning
System includes antialiasing filter, Sample-and-Hold amplifier, quantizer, and encoder.
Prevents aliasing of high-frequency signals, holds analog signal constant during conversion.
5.3. Resolution
Minimum change in signal for conversion is determined by the number of bits.
Resolution defined as 1/2^n, ratio of full-scale input voltage to resolution provides input voltage change associated with 1 LSB.
5.4. Quantisation and Analog Errors
Quantisation Error: Digital error due to resolution, leads to staircase waveform upon conversion back to analog.
Analog Error: Variations in switching points due to operational amplifier characteristics contribute significantly.
5.5. Linearity Error
Variation in voltage step size, expressed as a fraction of 1 LSB.
5.6. DNL and INL
DNL error arises when input levels for successive output codes deviate from 1 LSB.
INL reflects actual characteristics of A/D converter compared to ideal performance.
5.7. Dither Technique
Random noise added to input before conversion can improve A/D converter performance.
Causes oscillation in LSB state for low-level signals, enhances range at the cost of slight noise increase.
5.8. Conversion Time
Time required for A/D converter to complete analog to digital conversion.
5.9. Input Voltage Range
Range of voltage acceptable without causing overflow in digital output.
6. A/D Converter Types
6.1. Simultaneous Type A/D Converter
Fastest due to simultaneous comparison across multiple reference voltages; requires many comparators.
6.2. Flash Type A/D Converter
Simple design, but not suitable for more than 4 bits due to rapid increase in required comparators.
6.3. Successive Approximation ADC
Works by incrementally specifying the digital output based on comparisons with the unknown analog input.
Functional Block Diagram: Employs a successive approximation register (SAR) to find required values progressively.
7. 555 TIMER IC UNIT OPERATION
7.1. Circuit Design
Combination of linear comparators and digital flip-flops.
Operates within an 8-pin package, using three resistors for reference voltages.
7.2. States of Operation
Output states determined based on threshold and trigger levels.
8. Monostable and Astable Modes
8.1. Monostable Operation
Output is triggered by an input pulse, returns to original state upon reset.
8.2. Astable Operation
Continuous output oscillation generated without any external triggering; frequency controlled by resistor and capacitor values.
(same as before just in paragraph form)
MODULE V INTEGRATED CIRCUITS
1. ANALOG AND DIGITAL DATA CONVERSION
Signal measurement and analysis are crucial for determining characteristics of signals, with the analysis beginning at the signal acquisition phase. The most common method for acquiring signals is sampling, which involves capturing values at discrete times.
2. Signal Definitions
2.1. Analog Signal
An analog signal is defined over a continuous time interval, where its amplitude can take a continuous range of values.
2.2. Quantisation
Quantisation refers to the representation of a variable by a finite set of discrete values, thus a quantised variable can assume only a finite number of distinct values.
2.3. Discrete Time Signal
A discrete time signal is defined only at certain points in time, making the independent time variable quantised. A sampled-data signal results from sampling an analog signal at discrete intervals.
2.4. Digital Signal
A digital signal features both time and amplitude quantisation, represented by a sequence of words containing finitely many bits.
3. D/A & A/D Converters
3.1. D/A Converter (DAC)
A D/A converter converts digital data to equivalent analog data, commonly used to drive motors and analog devices.
3.2. A/D Converter (ADC)
Conversely, an A/D converter transforms analog data into equivalent digital data (in binary format), and both types of converters are available as monolithic integrated circuits.
4. SPECIFICATIONS OF D/A CONVERTER
4.1. Accuracy
Accuracy is crucial as components may experience drift, aging, and noise, leading to performance degradation. Absolute accuracy is defined as the maximum deviation of output from the ideal value expressed in fractions of 1 LSB. Errors can be classified into static (offset and gain errors) and dynamic errors.
4.2. Offset Voltage
An output should ideally be 0V when all bits are 0; however, a small output voltage (offset voltage) is often present. This offset error can be adjusted to ensure the output goes through the origin.
4.3. Linearity
Full-scale error is the maximum deviation of output from the expected value, expressed as a percentage of full scale. Linearity error refers to the maximum deviation in step size from ideal; a perfect D/A converter demonstrates equal increments in output for equal increments in input.
4.4. Differential Nonlinearity Error (DNL)
DNL measures the difference between the ideal output response and the actual output for successive D/A codes, where the ideal response produces output values exactly one code apart.
4.5. Integral Nonlinearity Error (INL)
INL reflects the deviation of an actual transfer function from a straight line after adjustment for offset and gain errors.
4.6. Monotonicity
A D/A converter is monotonic if the output increases with binary input without downward steps in the staircase output.
4.7. Resolution
Resolution is the smallest change in analog output for a change in digital input, calculated as the weight of the LSB. Percentage resolution is determined such that for an n-bit digital input, the total number of steps is (2^n – 1).
4.8. Settling Time
Settling time is the duration for the D/A output to stabilize within ±(1/2) LSB of the final value. It is affected by switching times, stray capacitances, and inductances.
4.9. Temperature Sensitivity
The analog output can vary with temperature; sensitivity ranges from ±50 ppm/°C to ±1.5 ppm/°C.
4.10. R2R Ladder D/A Converter
The R2R ladder D/A converter utilizes resistors of only two values, simplifying design by producing an output that is a weighted sum of digital inputs.
5. A/D CONVERTER
5.1. Conversion Process
An A/D converter converts an analog signal into an n-bit binary coded digital output by sampling the analog input at a frequency higher than the maximum input signal component.
5.2. Components and Functioning
The system comprises an antialiasing filter, a sample-and-hold amplifier, a quantizer, and an encoder to prevent aliasing of high-frequency signals and hold the analog signal constant during conversion.
5.3. Resolution
Resolution is defined as the minimum change in signal for conversion, determined by the number of bits. It is denoted as 1/2^n, where the full-scale input voltage to resolution provides the input voltage change associated with 1 LSB.
5.4. Quantisation and Analog Errors
Quantisation error results in a digital error due to resolution, leading to a staircase waveform upon conversion back to analog. Analog error represents variations in switching points attributed to operational amplifier characteristics.
5.5. Linearity Error
Linearity error indicates variation in voltage step size, represented as a fraction of 1 LSB.
5.6. DNL and INL
DNL arises when the input levels for successive output codes deviate from 1 LSB, whereas INL reflects the actual performance characteristics of the A/D converter compared to ideal outcomes.
5.7. Dither Technique
The dither technique involves adding random noise to the input before conversion to improve A/D converter performance. This causes oscillation in the LSB state for low-level signals, thereby enhancing the range at the cost of slight noise increase.
5.8. Conversion Time
Conversion time signifies the period required for the A/D converter to complete the analog to digital conversion.
5.9. Input Voltage Range
The input voltage range designates an acceptable voltage range without causing overflow in the digital output.
6. A/D Converter Types
6.1. Simultaneous Type A/D Converter
This type is the fastest, as it performs simultaneous comparisons across multiple reference voltages, thus requiring many comparators.
6.2. Flash Type A/D Converter
While the flash type has a simple design, it is unsuitable for more than 4 bits due to rapid increase in required comparators as bit count rises.
6.3. Successive Approximation ADC
The successive approximation ADC works by incrementally specifying the digital output through comparisons with the unknown analog input, using a functional block diagram that employs a successive approximation register (SAR) for the progressive finding of required values.
7. 555 TIMER IC UNIT OPERATION
7.1. Circuit Design
The 555 timer IC unit features a combination of linear comparators and digital flip-flops and operates within an 8-pin package, utilizing three resistors for reference voltages.
7.2. States of Operation
The output states of the 555 timer are determined based on the threshold and trigger levels.
8. Monostable and Astable Modes
8.1. Monostable Operation
In monostable operation, the output is triggered by an input pulse and returns to its original state upon reset.
8.2. Astable Operation
Astable operation generates continuous output oscillation without external triggering, with frequency controlled by resistor and capacitor values.