C1 repeatedly charges through R1 and R2 from one-third to two-thirds of the supply, then discharges through R2. The conventional two-resistor circuit produces a duty cycle above 50%. The graph shows settled cycles; the initial startup pulse is longer. The simulated supply rises over 1 µs at power-on.
f=ln(2)(R1+2R2)C11
Ideal one-third/two-thirds thresholds and negligible discharge resistance. The mapped LM555 circuit uses a behavioral timing model; real component tolerances and output loading can change the result.
Change the form inputs or click a component value on the schematic. Choose Try in CircuitSim to simulate the configured circuit.
