Ring oscillator two

Kick me! This ring oscillator consists of three MOSFET inverters connected in a loop. Initially the circuit is in the state of unstable equilibrium where all three voltages in the loop are at the mid-point between high and low. It takes a small amount of noise for one of the voltages leave the mid-point and rigger a domino effect where the noise is inverted and amplified around the loop. With an odd number of inverters in a chain, there is no stable state to which a circuit could settle. Oscillation builds up. As seen from current animations, capacitors charge through n-channel transistors and discharge through p-channel transistors. Smaller capacitors charge quicker, resulting in higher frequency oscillation frequency. With larger power supply transistors draw more current, also resulting in higher oscillation frequency. Make those adjustments and see how the circuit responds. Shake your mobile device to kick-start oscillation!

published 12 years ago