Session 2: Analog Basics

Modify the AND gate netlist to create an OR gate instead Hint: Swap the series/parallel arrangement of transistors

Schmitt trigger analysis: Look up a CMOS Schmitt trigger schematic and identify which transistors set the upper vs lower threshold

Optional: Build a simple circuit (LED + resistor + button) in TinkerCAD and observe current flow

Modify AND gate to make it and OR

Watched a YT video Transistor Logic Gates - NAND, AND, OR, NOR

Transistors - NPN & PNP - Basic Introduction

NPN & PNP Transistors explained - electronics engineering Did a sketch to rationalize it.

[Pic of sketch]

Need to sketch it and post.

Schmitt Trigger

YT Vid CMOS Schmitt trigger and its application

Took me a minute to figure out the circuit symbol bw PNP and NPN.

Need to sketch it and rationalize.

Build a Simple Circuit

I built a couple of different circuits to test out building and simulating circuits. I did all of this with TinkerCAD.

LED and Button

I used TinkerCAD to build and simulate my simple circuit. It was a pretty strightforward interface with graphic elements for common components. I started by making simple circuit with battery, switch, and LED. I connected the elements with wires in the interface. I was able to start the simulation using the “Start Simulation” button at the top of the interface. I was able to see the LED come on when I virtually pressedt the button.

I then added a multimeter to the sim so I could see the amp draw of the circuit. I added it after my resister and before the connection to the negative of the battery. Then I rant the simulation again and I was able to see that my circuit was drawing about 10mA of current.

Single Transistor Circuit

I then built a slightly more complicated circuit to explore transistors. I built a single transistor circuit with a button to control current flow to the gate pin. I added multimeters and LEDs to see the current at each part of the circuit.

When simulating this circuit I could see how the current flows though the transistor. When the button is off, no current flows and the LEDs are not on. When the momentary is pushed (as shown above) the LEDs turn on and current flows through the different legs of the circuit. The gate pin takes about 1/3 of the current and collector side takes roughly the other 2/3.

AND Gate

I took this one step further and tried to build and AND gate.

I used this Circuit Digest article as a guide to the layout. I kept the 9V battery and added another transistor. I used slide switches to control the gates of both transistors (mostly because I could never do both on with one mouse click) and added LEDs on all of the legs for visualization.

Then I ran through all of the logic scenarios and recorded the voltage at the output for each condition.

First Transistor	Second Transistor	Voltage	Logic Value
0	0	0.00	0
1	0	0.00	0
0	0	0.247	0
1	1	2.380	1

Generally this seemed to work out as planned. However, I am a little confused as to why there is some residual output voltage when the first transistor is low and the second is high. However it is not enough to change the logic output to high.

Below are the images of the other logic conditions of the circuit.

Circuit with input of 1 and 0.

Circuit with input of 0 and 1.

Circuit with input of 1 and 1.