Building Logic Gates with MOSFETs

flux

2:08

Project

Analyzing MOSFET gate building.

Clarifying component specifications.

Evaluating component-linking requirements.

Discussing transistor theory.

Planning CMOS logic design response.

Using Knowledge Base Tool.

Fetching design knowledge.

Awesome goal. Here’s a concise, practical path to building logic gates from MOSFETs, with what to watch out for when you turn this into real hardware.
  1. Pick your logic family
  • CMOS (recommended): complementary N-channel MOSFET + P-channel MOSFET. Advantages: near-zero static power, strong ‘0’ and ‘1’, good noise margin.
  • NMOS with resistor-load: a single NMOS pulls down; a Resistor pulls up. Simpler, but slow and burns static power.
  1. The CMOS inverter (your core building block)
  • Connections: PMOS source to VDD, NMOS source to GND, drains tied together as output, gates tied together as input.
  • Behavior:
    • Input = 0 V: PMOS ON, NMOS OFF → Output = VDD.
    • Input = VDD: PMOS OFF, NMOS ON → Output = 0 V.
  1. Build NAND and NOR from the inverter pattern
  • 2-input NAND:
    • Pull-up (PMOS network): PMOS in parallel (A or B can pull up).
    • Pull-down (NMOS network): NMOS in series (both A and B must pull down).
  • 2-input NOR:
    • Pull-up (PMOS): PMOS in series.
    • Pull-down (NMOS): NMOS in parallel.
  • XOR/XNOR: use combinations of NAND/NOR/INV, or transmission-gate style if you’re feeling adventurous.
  1. Practical rules that will save you time (authoritative best practices)
  • Do not let gates float. Always add a weak default gate pull-up or pull-down (as appropriate) so devices power-up safe and inputs don’t oscillate. A high-value Resistor per input works well.
  • Respect VGS limits. Avoid situations where the gate is driven in a way that makes VGS equal to -Vin or otherwise exceed the device rating; clamp or limit if needed.
  • Verify “logic level” at your supply. For PMOS parts, check that RDS(on) and drive are specified at your actual VGS (e.g., -3.3 V or -5 V), not only at -10 V.
  • Speed vs drive: large gate charge (Qg) slows edges and can overstress MCU pins. If you drive many MOSFET gates or big ones, consider buffering or adding small series gate resistors to tame dI/dt.
  • Layout and power integrity: use a solid ground plane, short connections, and decouple each gate cluster or IC with at least one 100nF Capacitor close to VDD-GND.
  • If building NMOS resistor-load logic: choose the pull-up to balance speed (lower value) vs power (higher value). It’s inherently slower than CMOS.
  1. Good starting point to practice
  • CMOS inverter at 5 V or 3.3 V using small-signal logic-level MOSFETs.
  • Measure the voltage transfer curve (Vout vs Vin), then chain two inverters to see fan-out effects.
  • Build 2-input NAND and NOR; then create AND/OR via gate + inverter combinations.
If you want, I can set up a small demo in your project: a CMOS inverter, NAND, and NOR, wired and ready to simulate/measure. Quick questions:
  • What supply voltage do you want (3.3 V or 5 V)?
  • Do you prefer CMOS (NMOS+PMOS) or a simpler NMOS-with-resistor-load for your first build?
Choose 5V CMOS
Start with inverter demo
Try NMOS resistor logic
Check gate resistor guidance
Learn Flux wiring basics
28 days

Ready.

Sign up to send
SOURCE
DRAIN
DRAIN
GATE
SOURCE
SOURCE
  • Ground
    Ground
    A common return path for electric current. Commonly known as ground.
    jharwinbarrozo
    20.5M
  • Net Portal
    Net Portal
    Wirelessly connects nets on schematic. Used to organize schematics and separate functional blocks. To wirelessly connect net portals, give them same designator. #portal
    jharwinbarrozo
    43.0M
  • Power Net Portal
    Power Net Portal
    Wirelessly connects power nets on schematic. Identical to the net portal, but with a power symbol. Used to organize schematics and separate functional blocks. To wirelessly connect power net portals, give them the same designator. #portal #power
    jharwinbarrozo
    11.4M
  • Generic Resistor
    Generic Resistor
    A generic fixed resistor for rapid developing circuit topology. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard resistor values: 1.0Ω 10Ω 100Ω 1.0kΩ 10kΩ 100kΩ 1.0MΩ 1.1Ω 11Ω 110Ω 1.1kΩ 11kΩ 110kΩ 1.1MΩ 1.2Ω 12Ω 120Ω 1.2kΩ 12kΩ 120kΩ 1.2MΩ 1.3Ω 13Ω 130Ω 1.3kΩ 13kΩ 130kΩ 1.3MΩ 1.5Ω 15Ω 150Ω 1.5kΩ 15kΩ 150kΩ 1.5MΩ 1.6Ω 16Ω 160Ω 1.6kΩ 16kΩ 160kΩ 1.6MΩ 1.8Ω 18Ω 180Ω 1.8KΩ 18kΩ 180kΩ 1.8MΩ 2.0Ω 20Ω 200Ω 2.0kΩ 20kΩ 200kΩ 2.0MΩ 2.2Ω 22Ω 220Ω 2.2kΩ 22kΩ 220kΩ 2.2MΩ 2.4Ω 24Ω 240Ω 2.4kΩ 24kΩ 240kΩ 2.4MΩ 2.7Ω 27Ω 270Ω 2.7kΩ 27kΩ 270kΩ 2.7MΩ 3.0Ω 30Ω 300Ω 3.0KΩ 30KΩ 300KΩ 3.0MΩ 3.3Ω 33Ω 330Ω 3.3kΩ 33kΩ 330kΩ 3.3MΩ 3.6Ω 36Ω 360Ω 3.6kΩ 36kΩ 360kΩ 3.6MΩ 3.9Ω 39Ω 390Ω 3.9kΩ 39kΩ 390kΩ 3.9MΩ 4.3Ω 43Ω 430Ω 4.3kΩ 43KΩ 430KΩ 4.3MΩ 4.7Ω 47Ω 470Ω 4.7kΩ 47kΩ 470kΩ 4.7MΩ 5.1Ω 51Ω 510Ω 5.1kΩ 51kΩ 510kΩ 5.1MΩ 5.6Ω 56Ω 560Ω 5.6kΩ 56kΩ 560kΩ 5.6MΩ 6.2Ω 62Ω 620Ω 6.2kΩ 62KΩ 620KΩ 6.2MΩ 6.8Ω 68Ω 680Ω 6.8kΩ 68kΩ 680kΩ 6.8MΩ 7.5Ω 75Ω 750Ω 7.5kΩ 75kΩ 750kΩ 7.5MΩ 8.2Ω 82Ω 820Ω 8.2kΩ 82kΩ 820kΩ 8.2MΩ 9.1Ω 91Ω 910Ω 9.1kΩ 91kΩ 910kΩ 9.1MΩ #generics #CommonPartsLibrary
    jharwinbarrozo
    1.5M
  • Generic Capacitor
    Generic Capacitor
    A generic fixed capacitor ideal for rapid circuit topology development. You can choose between polarized and non-polarized types, its symbol and the footprint will automatically adapt based on your selection. Supported options include standard SMD sizes for ceramic capacitors (e.g., 0402, 0603, 0805), SMD sizes for aluminum electrolytic capacitors, and through-hole footprints for polarized capacitors. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard capacitor values: 1.0pF 10pF 100pF 1000pF 0.01uF 0.1uF 1.0uF 10uF 100uF 1000uF 10,000uF 1.1pF 11pF 110pF 1100pF 1.2pF 12pF 120pF 1200pF 1.3pF 13pF 130pF 1300pF 1.5pF 15pF 150pF 1500pF 0.015uF 0.15uF 1.5uF 15uF 150uF 1500uF 1.6pF 16pF 160pF 1600pF 1.8pF 18pF 180pF 1800pF 2.0pF 20pF 200pF 2000pF 2.2pF 22pF 20pF 2200pF 0.022uF 0.22uF 2.2uF 22uF 220uF 2200uF 2.4pF 24pF 240pF 2400pF 2.7pF 27pF 270pF 2700pF 3.0pF 30pF 300pF 3000pF 3.3pF 33pF 330pF 3300pF 0.033uF 0.33uF 3.3uF 33uF 330uF 3300uF 3.6pF 36pF 360pF 3600pF 3.9pF 39pF 390pF 3900pF 4.3pF 43pF 430pF 4300pF 4.7pF 47pF 470pF 4700pF 0.047uF 0.47uF 4.7uF 47uF 470uF 4700uF 5.1pF 51pF 510pF 5100pF 5.6pF 56pF 560pF 5600pF 6.2pF 62pF 620pF 6200pF 6.8pF 68pF 680pF 6800pF 0.068uF 0.68uF 6.8uF 68uF 680uF 6800uF 7.5pF 75pF 750pF 7500pF 8.2pF 82pF 820pF 8200pF 9.1pF 91pF 910pF 9100pF #generics #CommonPartsLibrary
    jharwinbarrozo
    1.5M
  • Generic Inductor
    Generic Inductor
    A generic fixed inductor for rapid developing circuit topology. *You can now change the footprint and 3D model at the top level anytime you want. This is the power of #generics
    jharwinbarrozo
    15.5k
  • Terminal
    Terminal
    An electrical connector acting as reusable interface to a conductor and creating a point where external circuits can be connected.
    natarius
  • RMCF0805JT47K0
    RMCF0805JT47K0
    47 kOhms ±5% 0.125W, 1/8W Chip Resistor 0805 (2012 Metric) Automotive AEC-Q200 Thick Film #forLedBlink
    jharwinbarrozo
    1.2M
  • 875105359001
    875105359001
    10uF Capacitor Aluminum Polymer 20% 16V SMD 5x5.3mm #forLedBlink #commonpartslibrary #capacitor #aluminumpolymer #radialcan
    jharwinbarrozo
    1.2M
  • CTL1206FYW1T
    CTL1206FYW1T
    Yellow 595nm LED Indication - Discrete 1.7V 1206 (3216 Metric) #forLedBlink
    jharwinbarrozo
    1.1M

Properties

W
Ω

Pricing & Availability

Distributor

Qty 1

Assets

Texas_Instruments_-_CSD17575Q3T.step

Texas_Instruments_-_CSD17575Q3T.step

3D3D Model
n-channel-mosfet

n-channel-mosfet

n-channel-mosfetDefault

Controls