Beyond Arduino, Part 2: Analog Input Output

Discover why the analog world matters for sensors and devices, from accelerometers and glucose meters to touch screens and audio. See how analog readings and signals power microcontrollers and sensors.

Explore analog input and output in microcontrollers using real-world examples like heart monitors, screen brightness, temperature sensing, and automotive controls to convert world signals to digital measurements and back.

Compare analog and digital data by highlighting their infinite, continuous values versus finite, discrete values. Explore how real-world quantities like temperature, time, brightness, and voltage are represented digitally in computing.

Explore how analog and digital worlds differ in computing systems. See how analog to digital and digital to analog converters enable microcontrollers to capture and output signals.

Explain that an amplifier is a block that takes input voltage (and current) and outputs a modified voltage, increasing the signal amplitude across radio frequency, intermediate frequency, and audio amplifiers.

An amplifier multiplies the input signal by a constant factor, doubling its amplitude in the time plot, while distortions or phase shifts can alter the waveform.

Model the amplifier as a two-port system with input and output ports, analyzing voltages and currents to reveal internal parameters and four information-transfer models, including controlled and dependent power supplies.

Learn about dependent sources, including cccs, ccvs, vcvs, and vccs, and their gains and transfer units, including ohms, transfer impedance, and trans conductance.

Identify desired parameters: maximize input impedance and minimize output impedance to reduce current draw and voltage drop, with high gain A; note frequency performance varies, with ideal operation across frequencies.

Explore cascade architecture where each block feeds the next and loads like speakers, antennas, heaters, or motors, powered by an external dc supply through positive and negative terminals.

Explore what an op-amp is and how it enables comparators, inverting and summing amplifiers, and acts as the core of analog-to-digital and digital-to-analog converters.

Explain the ideal op-amp model with differential input, high input resistance, open loop gain AOL, and low output impedance, and how an open circuit yields no current.

Examine ideal op-amp characteristics: infinite input impedance, zero output impedance, and infinite open-loop gain and maximum operating frequency, while recognizing these goals are unattainable in practice.

Explore the five basic op-amp characteristics, including high input impedance, low output impedance, high open-loop gain, and microvolt output when inputs are shorted, achieved by integrated circuits.

Examine the LM 741 op amp’s pinout, supply pins, and offset nulls, and see how its differential amplifier and current mirrors shape the output.

Explore how an op amp functions as a voltage comparator, comparing non-inverting and inverting inputs against a reference to yield positive or negative saturation at the output.

Explore how saturation voltages limit an amplifier's output, showing how pull-up and pull-down transistors create voltage drops that prevent reaching supply levels for positive and negative swings.

Explain why an op amp with high open-loop gain drives output to saturation due to input difference between non-inverting and inverting terminals, and how supply rails limit the result.

Learn how a potentiometer provides a voltage from 0 to 5 volts and how a comparator evaluates whether this input exceeds a reference, producing a high or low saturation output.

Analyze a light-sensing circuit using a photo transistor where light intensity modulates current through a resistor, creating an output voltage that inversely relates to light intensity.

Understand why sensor voltages like 3V and 4V may not meet TTL gate thresholds (low ~0.8V, high ~2.1V) and see how a comparator converts analog signals into valid logic levels.

Compare the sensor voltage with a comparator set to a 3.5-volt reference, then feed the result into a gate to produce a 0/5-volt output.

Plot the comparator output voltage against the sensor signal, showing how the output switches from zero to supply voltage when the input crosses the reference.

Explore negative feedback in an inverting amplifier, where part of the output feeds back to the inverting input through a feedback loop, keeping the output within saturation and promoting stability.

Explore how the ideal op-amp's infinite input impedance and limited output swing enable simple circuit analysis, then derive a current equation at the focus node.

Demonstrate kcl node analysis by equating input and feedback currents at a node, concluding that the feedback current equals the negative of the input current.

Explore virtual ground and how tiny input voltages yield a modest five-volt output via input and feedback resistances; analyze input and feedback current under high open-loop gain.

Derive Vout from Vin with basic algebra, showing an inverting amplifier outputs minus a constant times the input and allows easy, nearly ideal gain control via the feedback resistance.

Explore the virtual ground concept in op-amp circuits: assume zero input current due to high input impedance, and use negative feedback to keep the input voltage near zero, simplifying analysis.

Analyze a two-port black-box amplifier and relate voltage gain, current gain, input impedance, and output impedance to a circuit model for the inverting amplifier.

Derive gain as minus feedback resistance over input resistance, and model the circuit as a Tuborg network to analyze virtual ground and output voltage as a divider with output impedance.

Analyze input impedance from input resistance and output impedance in an inverting op-amp, where output impedance lies in parallel with the feedback resistance and current gain depends on the load.

Explore digital to analog conversion as a fundamental data conversion and how binary weighted DACs use duty cycle variation to connect digital systems with the analog world.

Master pulse width modulation by varying duty cycle to convert digital signals into analog output; use a timer and a low-pass filter to smooth the result.

Examine the typical dac daisy pinout, including digital input bits, reference voltage, and output limits from zero to vref, with ground or differential input options.

Investigate a binary weighted dasi built with a summing amplifier and digitally controlled analog switches, using weights from half to one sixteenth and Vref, plus inversion for practical higher-bit expansion.

Explore the r-2r dac, a resistor ladder that uses 2r and r segments to synthesize output voltages, simplifying feedback networks and matching the doubled-resistance approach.

Analyze parallel and series resistor combinations in the R-2R DAC circuit to derive the overall equivalent resistance and simplify the network.

Transform the r-2r dac input into Thevenin equivalents, showing an inverting amplifier with gain minus one and output minus vref over two, where the msb weight is half of vref.

R-2R DAC advantages include using a single resistor value with matched and doubled resistors, reducing components; enables fast, binary-weighted conversion with instant output changes and compact circuitry.

Explore analog to digital conversion, including what it means, flash converters, and the popular successive approximation ADC, with examples of discrete versus continuous data and encoding.

Explain how an analog-to-digital converter converts an analog input to a digital output using a 10-bit encoding, with reference voltages and linear mapping.

Explore encoding in analog-to-digital conversion, illustrating a 3-bit ADC mapping input voltages to binary codes, with full-scale range, reference levels, and least significant bit changes.

Explore the flash ADC, the fastest analog-to-digital converter built from a resistive network, parallel comparators, and fast logic, producing a 3-bit conversion from a 5 volt reference.

This flash adc example compares a 3-volt input with several reference levels using comparators; an encoder maps the highest zero to a three-bit binary number, outputting four.

The flash adc uses a priority encoder to select the highest zero level, requiring many comparators and heavy circuitry; it is fastest but least efficient in space and power.

Discover the successive approximation analog to digital converter, the most popular ADC, and understand its efficient algorithm compared with the flash ADC, including its fit for microcontroller platforms.

Explore how a closed-loop adc uses a sample-and-hold, comparator, and a successive approximation register driven dac to compare input voltage against a voltage reference in a clocked feedback loop.

Explore the successive approximation register as a state-machine that narrows the digital representation of an analog input by comparing values and converging on the ADC result.

Demonstrate a four-bit ADC using a successive approximation register to narrow a 10-volt input against a 12-volt reference, explaining binary weights and fixed-point concepts.

Explore how a successive approximation register narrows an input voltage by testing each bit against a reference, updating the DAC output, and signaling end of conversion for a microcontroller.

Explore an iterative algorithm that runs one cycle per bit, producing 16 values with four bits and 1024 with ten bits, logarithmic time and a binary-search in the analog world.

Follow a time diagram of a 12-bit SAR ADC, where a DAC outputs voltages and a binary search narrows input between ten point five and nine point seventy five volts.