Abstract: A variable capacitor modulator for use in a voltage controlled oscillator, includes a differential varactor block, coupling capacitors for connecting nodes of the varactor block to a tank circuit, and an element connected between the respective nodes and ground to trim the gain of the variable capacitor modulator.

Abstract: An amplifier, suitable for radio frequency applications, has good noise properties because of a special transistor configuration. A pair of transistors is connected in a cascode configuration, to overcome the Miller effect. The transistors have their bases driven by a common current source. The main current paths from ground to each of the output terminals are essentially noise-free. One of the transistors, acting as a transconductance amplifier, does introduce some noise though this is minimized by the use of an inductor. A third transistor forms a current source for the current path to one of the output terminals. A differential output is achieved at the output terminals because the pair of transistors has complementary outputs. In another embodiment, a capacitor is connected across the collector and base electrodes of one of the transistors to introduce a further stage of gain.