74HC4066 is a quad bilateral analog switch IC made using High-Speed CMOS technology.
In simple words:
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It has 4 independent switches inside one chip.
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Each switch can connect or disconnect two pins based on a control signal (just like turning ON or OFF a real switch).
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It can pass both analog and digital signals.
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It is called "bilateral" because the signal can flow in both directions — from A to B or from B to A.
🔌 How it Works
Each switch inside the 74HC4066 has:
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2 I/O pins → (let’s call them "A" and "B")
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1 control pin → (let’s call it "Enable" or "Control")
| Control Signal | Behavior |
|---|
| HIGH (logic 1) | Connects A and B |
| LOW (logic 0) | Disconnects A and B |
So, if you apply a HIGH signal to the control pin, the switch "closes," and the signal (analog or digital) flows freely between the two pins.
If the control is LOW, the connection is "open," and no signal passes through.
🎯 Key Features of 74HC4066
| Feature | Detail |
|---|---|
| Supply voltage (Vcc) | 2V to 6V (typically 5V) |
| Max signal range | Vcc (can't pass voltages bigger than Vcc) |
| On-resistance (RON) | About 70Ω typical at 5V |
| Fast switching | Yes, because it’s high-speed CMOS |
| 4 switches per IC | Yes |
| Bilateral switching | Yes (signal can flow both ways) |
| Passes analog & digital signals | Yes |
🧩 Typical Applications
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Audio switching (for example: selecting different audio sources)
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Digital logic signal routing
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Analog multiplexers/demultiplexers
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Creating simple digital selectors
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Microcontroller projects for switching sensors or devices
📦 74HC4066 IC Pinout (basic idea)
| Pin No | Name | Description |
|---|---|---|
| 1 | Control 1 | Control for switch 1 |
| 2 | I/O 1A | First side of switch 1 |
| 3 | I/O 1B | Second side of switch 1 |
| ... | ... | (same pattern for others) |
| 14 | Vcc | Power Supply (e.g., 5V) |
| 7 | GND | Ground |
🖍️ Visual:
Imagine the inside of 74HC4066 like 4 small solid-state "relays" (no moving parts), all controlled individually.
| Control | Switch | A | B |
|---|
| HIGH | Connected (ON) | Signal flows |
| LOW | Disconnected (OFF) | No signal |
🚀 In brief:
74HC4066 = 4 small ON/OFF switches inside a chip, controlled by logic signals, capable of passing both analog and digital voltages up to Vcc. The Arduino PID Temperature Controller tutorial show you a real small circuit using CD4066 which is same as 74HC4066 to turn on and off an oven.
