The use of quantum well devices for extremely high frequency oscillators has recently been proposed. Results up to 200 GHz have been reported. although the output powers have been extremely small. We present analyses of a new quantum well oscillator device, the quantum well injection transit time (QWITT) diode, which exploits transit time effects to improve rf performance of quantum well oscillators. The small and large signal analyses indicate that a QWrrr diode may provide reasonable power levels at frequencies above 100 GHz.