Emitter-coupled oscillator with two cross-coupled transistors - has collector loads formed by diode and controlled transistor respectively

摘要

The oscillator has two cross-coupled transistors (T1, T2) whose emitters are supplied from separate current sources (S1, S2). A capacitor or a quartz crystal couples the emitters of the transistors together. The output voltage is taken from the transistors' collector. The load resistor of the second transistor is formed by the collector/emitter path of a third transistor (T4) whose base is coupled to the collector of the first transistor. The load resistor for the first transistor is a fourth transistor connected as a diode (D1). Alternnatively, both the first and second transistors may have controlled transistors are load resistors: in this case the bases of these load transistors are connected to a third current source and the base/emitter junctions of both load transistors are shunted by another transistor acting as diode.