Part of the Day · NE555 — SOIC-8 timer IC

Part of the Day · 2026-10-23

The most famous timer IC, generating pulses and time delays with a few resistors and one capacitor. Its single output can sink or source up to 200mA, so it drives LEDs and buzzers directly. The TI SOIC-8 (D) part is marked NE555.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOIC-8 · top view · approx. 15×)

Pins 1 GND (ground) · 2 TRIG (trigger input) · 3 OUT (output) · 4 RESET (reset, active Low) · 5 CONT (control voltage) · 6 THRES (threshold input) · 7 DISCH (discharge) · 8 VCC (supply)

Package SOIC-8

Key specifications

Values are from the Texas Instruments datasheet.

Marking and pins

Typical uses

• LED flasher, buzzer oscillator (astable mode)
• Delay timer that stays on for a set time after a button press (monostable mode)
• PWM / pulse generation, frequency division

Companion & similar parts

• NA555 — Wide-temperature version from the same datasheet (-40 ~ 105℃)
• SA555 — -40 ~ 85℃ version from the same datasheet
• SE555 — -55 ~ 125℃ version from the same datasheet, supply up to 18V

The datasheet recommends tying unused inputs to an appropriate logic level. When RESET (pin 4) is Low the output is held Low, so keep it High (VCC) when unused. With a 5V supply the output is compatible with TTL inputs.