IF Amplifier using C/SUB c/ compensated transistors

An integrated bridge network of four transistors is used as a self-neutralized active element in tuned RLC amplifier designs. The bridge network compensates for the transistor collector-base junction capacitance (C/SUB c/), yielding a 95-percent reduction in the common-emitter reverse transmission admittance. IF amplifier stages that achieve the maximum unilateral power gain of a common-emitter transistor while maintaining excellent alignability are realized using the C/SUB c/ compensated transistor structure. Variations of the relative bias current levels of the transistors in the bridge network provides gain control by way of signal cancellation. This technique produces minimal frequency response variations of the amplifier stage being controlled. A noise analysis shows output signal to noise ratio at maximum attenuation can be a performance limitation.