Calculadora de Constante de Tempo
Resposta transitória RC e RL
Required Parameters
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Quick Answer
The time constant (τ) determines how fast an RC or RL circuit responds to a step change. RC: τ = R×C. RL: τ = L/R. After 5τ, the circuit has settled to 99.3% of its final value.
Calculadora de Constante de Tempo
Calcule a constante de tempo RC ou RL (tau) para circuitos de carga e descarga.
Constante de Tempo RC
tau = R x C
| Tempo | % Carregado | % Restante |
|---|---|---|
| 1 tau | 63,2% | 36,8% |
| 2 tau | 86,5% | 13,5% |
| 3 tau | 95,0% | 5,0% |
| 5 tau | 99,3% | 0,7% |
Constante de Tempo RL
tau = L / R
Ferramentas Relacionadas
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Design Notes
The time constant connects two fundamental domains: time response and frequency response. A circuit with τ = 1ms has a bandwidth of fc = 1/(2πτ) = 159 Hz. This means slower circuits (larger τ) filter more noise but respond more sluggishly to input changes. In digital design, minimizing parasitic RC (stray capacitance × trace resistance) is critical for achieving fast rise times: t_rise ≈ 2.2τ.
Common Mistakes
- 1
Forgetting that RL and RC time constants have opposite dependencies on R — increasing R makes RC slower but RL faster.
- 2
Assuming the circuit reaches final value after one time constant. One τ only reaches 63.2% — you need 5τ for practical completion.
- 3
Not accounting for source impedance when calculating the time constant of an RC network driven by a non-ideal source.
Engineering Handbox
1. τ = R × C = 10,000 × 47 × 10⁻⁶ = 0.47 seconds 2. Time to 95%: 3τ = 1.41 seconds 3. Time to 99.3%: 5τ = 2.35 seconds 4. Cutoff frequency: fc = 1/(2π × 0.47) = 0.339 Hz
Knowledge Base
O que é a constante de tempo (τ)?
O tempo para o circuito atingir 63,2% do valor final. RC: τ = R×C. RL: τ = L/R.
Quantas constantes de tempo para carga completa?
1τ=63,2%, 2τ=86,5%, 3τ=95%, 5τ=99,3%. Após 5τ, considera-se estabilizado.
Equação de tensão na carga?
V(t) = V_final × (1 - e^(-t/τ)) na carga, V(t) = V_inicial × e^(-t/τ) na descarga.
Relação com frequência de corte?
fc = 1/(2πτ). Maior constante de tempo = menor frequência de corte.
Importância para debounce?
Chaves mecânicas saltam 1–10ms. Filtro RC com τ = 5–10ms suaviza os saltos.
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