Intro to Op-Amps

The operational amplifier or op-amp for short is an extremely useful electronic component that allows for the amplification of signals. For example, if you had a sensor that translates some physical change to an electrical change (a signal), but the signal was very small you could use an op-amp to amplify that signal without distorting it.

Today we are just going to input a dc signal into the op amp and measure its amplification. We'll get familiarized with the circuit setup and connect the theory with the real thing.

Pre-Requisites: Flea-Scope: Getting Started (Instructable created by me), Completion of ECE102

Op-Amp Chip(LMT358N), Power Supply, Resistors, Jumpers, Multimeter, 9V Battery

The two simplest practical op-amp configurations are the inverting and non-inverting configurations. The configurations can be derived using Kirchoff's current law (KCL) and you'll learn more about them in depth in your Circuits 1 course. The op-amp chip I'll be using has limitations so that we cannot get a negative Vout value, thus the inverting configuration will be off the table, but we can still observe the effects of the non-inverting configuration with the chip available.

Set up the circuit as seen above and we will be using two 10k resistors so that we can achieve a gain of 2 (Check non-inverting op amp equation to confirm). Before we start doing the real testing we'll record the voltage of our dc battery and ensure we get the values we expect. In my case the "9V" battery I had was actually 3 volts and if we apply a gain of 2 to the battery which is our input voltage we will expect an output voltage of 6V. Now lets see!

Always be cautious with power supplies and it is best practice to set your circuit up before you apply power to it. The images above demonstrate how I connect power and ground wires to a breadboard and then to our previously built circuit. After this is accomplished, I set the power supply to a value that ensures we won't have clipping. What I mean by this is that we do not want our power supply to be less than or really too close to our expected output voltage or it will cap off the output voltage at a different value than we calculated.

Use the multimeter to measure the output voltage by placing one probe at the output and the other at ground. The value above is what I measured and it's about 2 times my input voltage which was what I theoretically calculated.