▶ Watch: Brief History of Op-Amp Usage (10:07)
▶ Watch: Op-Amp Basics (5:11)
Modern processors and electronics typically use 0..5V supply voltages, which imposes certain limitations on amplifier circuits and components. Op-amp amplifiers are supplied with 0..5V single-ended power, so negative signals cannot be used. This significantly limits available circuit configurations compared to traditional ±15V dual-supply systems.
The operational amplifier (op-amp) has been and remains a fundamental electronic component, especially in embedded systems (such as Arduino). It has played a crucial role in the design and implementation of analog computers and many other technical devices. Today, however, many functions that previously required op-amps can be replaced by small computers.
Therefore, this workshop focuses on a few circuit configurations that still have great practical significance. The key concept is how to obtain signals from various sensors (typically in the 0..5V or 0..3.3V range) that the processor's ADC (analog-to-digital converter) can read. We concentrate on circuits needed around the Arduino development environment, focusing primarily on analog DC signals, while AC signals and audio applications are excluded from the scope.
This workshop also introduces new tools for circuit analysis: the oscilloscope and the 555 signal generator. Additionally, we will explore RLC circuit analysis, which provides fundamental understanding of reactive components and their behavior in electronic circuits.
▶ 555 Timer Circuit
▶ Affordable Portable Oscilloscope and Usage
▶ YouTube - EasyEDA Tutorial for Beginners
▶ YouTube - EasyEDA Tutorial for Beginners
This workshop covers the following op-amp circuits:
First of all, the purpose is to investigate resonance as a phenomenon. The first image is just the idea of the circuit. That is, we do not have information about the values of individual components (C and L), but we know that this connection is an oscillating circuit. However, we have at our disposal a small oscilloscope, components, and a small 555 circuit that gives us a square wave. The purpose of this first task is to find the frequency at which the circuit begins to oscillate.
Below are images of a signal generator (555-based) and various oscilloscopes that come with the course materials. By clicking on the images, you can access YouTube instructions.
⚠️ Warning: Do not connect to mains power, but test the 555 pulse generator.
Tip: Press the AUTO button.
Task: Build a voltage follower circuit. Check the datasheet for pin positions. Test by inputting a signal from a 555 circuit and examine the output.
Build a voltage divider that allows you to adjust the output voltage of the 555 circuit. Use a potentiometer. Test as shown in the image.
You will need a 555 circuit, the output voltage of which you can adjust in the next task.
Task: Build both inverting and non-inverting amplifier circuits. Test them with signals from the 555 circuit and examine the output with an oscilloscope.
P.S. Use a rail-to-rail op-amp amplifier; it can utilize the voltage range close to the supply voltage.
1. Did you get the non-inverting amplifier working with the 555 circuit and voltage divider?
2. Did you get the inverting amplifier working? If you did, that's a problem. It shouldn't work, because the input voltage is positive but the output voltage is negative. However, we don't have a negative power supply for the op-amp. If you passed anyway, move on to the next task: level shifting.
In order to combine the level shift and amplification need much more effort. The following circuit is simulated. The input is small sin wave amplitude on 0.01V peak to peak.
Simulated outcome of small ±0.01Volt input (Yellow) to amplified and shifted to ADC-converter (accept signal from 0..5V).
There are many filters in the world, both passive and active. Below are the two most important: lowpass and highpass filters, both passive and active.
Cutoff frequency: fc = 1/(2πR1C1)
Cutoff frequency: fc = 1/(2πR1C1)
Bode plots showing the frequency response of the filters. Magnitude shows gain in dB, phase shows phase shift in degrees.
Input signal: sine wave 0-5V (DC offset 2.5V, amplitude ±2.5V). Select frequency to see how filters affect the output amplitude.
Convert between Bode magnitude (dB) and amplitude (V). Reference: Input AC amplitude = ±2.5V (from 0-5V sine wave).
555 Timer Calculator: Calculate frequency, Time High, and Time Low for 555 timer circuits
Tip: Google "555 astable fritzing"
The 74C14 is a hex Schmitt trigger inverter integrated circuit. It contains six independent Schmitt trigger inverters, each with hysteresis characteristics that make it useful for debouncing switches, shaping waveforms, and creating oscillators.
Unlike standard inverters, the Schmitt trigger has two different threshold voltages: a higher one for rising edges and a lower one for falling edges. This creates a "dead zone" that helps eliminate noise and provides clean transitions.
Main uses include:
For more detailed information, visit: Talking Electronics - 74C14 Guide
Simulation of 74HC14 Schmitt Trigger showing the hysteresis effect on a noisy input signal.
The 74C14 has the following typical threshold values:
These values may vary slightly depending on the manufacturer and supply voltage.
DO NOT USE 9V Battery! (max 5V is allowed).
Calculate the time period of the output signal from a 7414 Schmitt trigger oscillator. The formula is: frequency = 1.2/(R × C)
Circuit Simulator: Falstad Circuit Simulator - Interactive circuit simulation with examples
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