The description of the phase shift oscillator:
http://www.allaboutcircuits.com/vol_3/chpt_9/4.html
says that the three RC sections each provide 60° of phase shift, but this is not true. As Chet Paynter says:
http://wps.prenhall.com/chet_paynter_introduct_6/0,5779,426330-,00.html
"You would think that each RC network in the phase shift oscillator would produce a 60° phase shift (3 × 60° = 180°), but this is not true. Each RC circuit loads the previous RC circuit, so their phase shifts are not equal. However, the total phase shift must equal 180° for the circuit to operate as an oscillator."
http://www.allaboutcircuits.com/vol_3/chpt_9/4.html
says that the three RC sections each provide 60° of phase shift, but this is not true. As Chet Paynter says:
http://wps.prenhall.com/chet_paynter_introduct_6/0,5779,426330-,00.html
"You would think that each RC network in the phase shift oscillator would produce a 60° phase shift (3 × 60° = 180°), but this is not true. Each RC circuit loads the previous RC circuit, so their phase shifts are not equal. However, the total phase shift must equal 180° for the circuit to operate as an oscillator."