Abstract: A wideband amplifier comprises a dual-emitter bipolar transistor arrangement with coaxial transformers, each having a high turns ratio and tight coupling between a first toroidal winding on an annular ferrite core and a second, single-turn, winding constituted by a metal container of the transformer. The second windings are coupled between respective emitters and signal ground, and the first windings are connected between the transistor base and collector, respectively, and signal ground. An input signal is supplied to the base, and an output signal is derived from the collector. The dual-emitter bipolar transistor, which has four terminals, is thereby transformed into a two-port (input port and output port) device which facilitates impedance matching, provides a linear and constant gain over a large bandwidth, provides high isolation of the input from the output, and provides low noise at the input and a high level at the output.

Abstract: A delay equalizer includes an amplifier with differential inputs, to which an input of the equalizer is coupled via first and third impedance circuits, and which are coupled to circuit ground via second and fourth impedance circuits, respectively. One of the first and second impedance circuits is constituted by a resistor, the other by a frequency-dependent network consisting of one or more tuned network sections. The third and fourth impedance circuits can similarly be a frequency-dependent network and a resistor or, desirably, two resistors. The amplifier can be a bipolar transistor whose base and emitter form the differential inputs. The equalizer can also include input and output impedance-matching amplifier stages, which may also provide amplitude equalization.

Abstract: A coaxial transformer is employed to provide impedance matching for the input of a bipolar transistor operated in the VHF frequency range. The coaxial transformer comprises a first winding wound around a ferrite toroidal core. The second winding has a single turn and consists of a metal enclosure substantially surrounding the first winding. One end of the first winding is connected to the base of the transistor and the other end of the first winding is connected to ground. One end of the second winding is connected to the emitter of the transistor and the other end of the second winding is connected to ground.