differential pair

First, sorry for the bad english. It's not the first time I've been looking for help on this circuit on the forum. I'm from Brazil, I'm doing a university project using which basically consists of using a colpitts oscillator with differential pair, with a SAW sensor in its feedback loop. The SAW...

First, sorry for my bad english. I'm building a project using a Colpitts Oscillator with Differential Pair, designed for ~117.6MHz. I'm using LTspice for simulation. The oscillator individually oscillates, but I need it to oscillate when I add a sensor model (as seen in the image in the...