Here is a simple get decent triangular wave oscillator for use in class d amplifiers:
http://i.imgur.com/yZlS0Tz.png?1
It is based on this circuit: 555 Delta-Sigma Modulator - Transwiki
http://i.imgur.com/yZlS0Tz.png?1
It is based on this circuit: 555 Delta-Sigma Modulator - Transwiki