Series Tuned Methods in Transistor Radio Circuitry

Series resonant LC networks can be effectively utilized in transistor-tuned amplifiers and oscillators to achieve simplicity of circuitry coupled with excellent performance. A new method for designing intermediate frequency transistor amplifiers is described. Series resonant LC elements are employed in the emitter circuits of the transistors along with direct coupling of the amplifier stages to achieve a relatively simple and stable amplifier. A transistor oscillator which employes series resonant tank circuit elements is also described. A high degree of frequency stability is realized without the use of elaborate nonlinear compensation techniques. Tests made on an uncompensated circuit indicate a frequency stability of about six parts per million per 10 per cent variation in supply voltage. The circuit configuration of both the amplifier and oscillator permits the design of units in which the operating frequency is almost independent of transistor properties and supply voltage. Analyses of circuit operation and experimental results are given for both the amplifier and oscillator applications.