Is pin 3 in the 7400/7402/7404/7408 chips an input or an output?
Fast Answer: Logic Gate Pinout & Configuration
- 7400 (NAND): Pin 3 is an Output.
- 7402 (NOR): Pin 3 is an Input.
- 7404 (NOT): Pin 11 is an Input.
- 7408 (AND): Contains Four (4) Quad 2-Input gates.
Technical Specifications Table: 7400 Series Logic ICs
The following table summarizes the pin functions and gate density for the standard 14-pin DIP (Dual In-line Package) configurations of these TTL logic chips.
| IC Model | Logic Function | Pin in Question | Function (I/O) | Total Gates |
|---|---|---|---|---|
| 7400 | Quad 2-Input NAND | Pin 3 | Output (1Y) | 4 |
| 7402 | Quad 2-Input NOR | Pin 3 | Input (1B) | 4 |
| 7404 | Hex Inverter (NOT) | Pin 11 | Input (6A) | 6 |
| 7408 | Quad 2-Input AND | N/A | N/A | 4 |
7400 Quad 2-Input NAND Gate Pinout
In the 7400 IC, pins 1 and 2 serve as inputs for the first NAND gate, while Pin 3 acts as the output. This pattern repeats throughout the chip for the remaining three gates. Standard TTL datasheets (Texas Instruments, Fairchild) confirm Pin 3 is the result of the NAND operation of Pins 1 and 2.
7402 Quad 2-Input NOR Gate Pinout
The 7402 IC has a different pin arrangement compared to some other quad gates: for gate 1, Pin 1 is the output, and Pins 2 and 3 are the inputs. That means Pin 3 is an input for the first NOR gate.
7404 Hex Inverter (NOT) Gate Configuration
The 7404 contains six independent NOT gates (inverters). Each gate uses two pins: one input and one output. Following the standard mapping, Pin 11 is the input (6A) for the sixth inverter, while Pin 10 is its corresponding output (6Y).
7408 Quad 2-Input AND Gate Capacity
The 7408 IC is a "Quad" package, meaning it houses four (4) independent AND gates. Each gate requires two input pins and one output pin.
- Gate 1: Pins 1, 2 (Inputs) -> Pin 3 (Output).
- Gate 2: Pins 4, 5 (Inputs) -> Pin 6 (Output).
- Gate 3: Pins 9, 10 (Inputs) -> Pin 8 (Output).
- Gate 4: Pins 12, 13 (Inputs) -> Pin 11 (Output).
Notes and References
- Pin numbering follows the conventional 14-pin DIP orientation: pin 1 is the first pin after the notch and pin 14 is VCC. GND is typically pin 7.
- Always consult the specific manufacturer's datasheet (SN7400, SN74LS00, SN74HC00, etc.) for exact electrical characteristics and variants.
References: Texas Instruments datasheets for SN7400/SN74LS00, SN7402/SN74LS02, SN7404/SN74LS04, SN7408/SN74LS08.