Formulas - Multivibrator

Monostable Multivibrator

Circuit diagram monostable multivibrator.

The switching time T of a monostable multivibrator is calculated by... $$T = R_2 C_1 ln(2) \approx 0.693 \times R_2 C_1$$  

Special cases monostable multivibrator with Timer NE555... $$T \approx 1.1 \times R C$$     monostable multivibrator with C-MOS 4098... $$T \approx 0.5 \times R C$$

Astable Multivibrator

Circuit diagram astable multivibrator.

The switching times \(\tau_i\) of an astable multivibrators is calculated by... $$\tau_1 = R_2 C_1 ln(2) \approx 0.693 \times R_2 C_1$$ $$\tau_2 = R_3 C_2 ln(2) \approx 0.693 \times R_3 C_2$$ The oscillation t... $$t = \tau_1 + \tau_2$$ and the frequency f... $$f = {1 \over t} = { 1 \over {\tau_1 + \tau_2}}$$  

Special cases astable multivibrator with Timer NE555... $$\tau_1 \approx 0.7 \times (R_1 + R_2) \times C_1$$ $$\tau_2 \approx 0.7 \times R_2 C_1$$     astable multivibrator with NOT gates... $$t \approx 2.2 \times R C$$