How to build a 555 Astable Oscillator Circuit Diagram. The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation,. Astable (free-running) mode: The 555 can operate as an oscillator. This free-running multivibrator uses an external current sink to discharge the timing capacitor, C. Therefore, interval ^ may easily be 1000 the pulse duration, t1( which defines a positive output. Capacitor voltage, V^, is a negative going ramp with exponential rise during the pulse output periods. This as is has low duty cycle.
555 Astable Oscillator Circuit Diagram