Frequency Stability of Point-Contact Transistor Oscillators

Frequency-stability properties of oscillators using point-contact transistors are investigated both analytically and experimentally. Point-contact-transistor "two-terminal" oscillators are analyzed by means of nonlinear differential equations of the Van der Pol type. Duality relationship is demonstrated between oscillators using the voltage-controlled, negative-impedance, base-input characteristics and oscillators using the current-controlled, negative-impedance, emitter-input or collector-input characteristics. As a result, the general stability criteria derived for the former can be applied directly to the latter. Stabilization techniques are derived according to theoretical analysis. Experimental results confirming the theoretical findings are also included.