Frequency
480.00 Hz
Duty
66.7%
Period
2.083 ms
e.g. 0.0000001 = 100nF, 0.000001 = 1µF
Frequency
480.00 Hz
Period
2.083 ms
Duty Cycle
66.7%
t(high)
1.386 ms
t(low)
693.00 µs
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Inputs
Result
f = 1.44/((10000+20000)×0.0000001) = 1.44/0.003 = 480Hz. Duty = (10000+10000)/(10000+20000) = 66.7%.
Inputs
Result
T = 1.1 × 10000 × 0.0001 = 1.1 seconds.
In astable mode, the 555 oscillates continuously. Frequency = 1.44 / ((R1 + 2×R2) × C). The output alternates between high and low, with duty cycle determined by R1 and R2 ratio.
| R1 | R2 | C | Frequency | Duty Cycle |
|---|---|---|---|---|
| 10kΩ | 10kΩ | 100nF | 480 Hz | 66.7% |
| 1kΩ | 10kΩ | 100nF | 686 Hz | 52.4% |
| 10kΩ | 10kΩ | 1µF | 48 Hz | 66.7% |
| 100kΩ | 100kΩ | 10nF | 480 Hz | 66.7% |
Monostable produces a single pulse when triggered. Pulse width T = 1.1 × R1 × C. After the pulse, output returns low until triggered again.
Basic astable always exceeds 50%. For 50%, add a diode across R2 so charge and discharge paths are equal, or use R1 much smaller than R2 to approach 50%.
Ceramic caps (100pF–100nF) for high frequencies, film caps (1nF–1µF) for audio, electrolytics (1µF–100µF) for low frequencies. Avoid electrolytics above 10kHz due to ESR.
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Last Updated: Mar 20, 2026
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