Abstract: An RF amplifier system having closed cavity containing an amplifying device that includes at least a cathode, an anode and a grid and wherein the amplifying device exhibits an internal grid-to-anode capacitance. Apparatus is presented for use in neutralizing the internal capacitance. This includes a feedback circuit including an external capacitor of fixed value and a phase inverting transformer having a transformer primary winding connected in series with the capacitor to the cathode. The transformer has a secondary winding connected between the cathode and the grid for supplying a phase inverted negative feedback voltage to the grid for neutralizing the cavity by the feedback voltage. The transformer coupling is adjustable to vary the magnitude of the feedback voltage.

Abstract: A cathode-follower power output stage is driven by a novel drive stage to provide with low distortion the large signal required to drive the output stage. The drive stage comprises two series connected vacuum tubes which share the large static and dynamic voltages of the drive stage so as to provide a drive signal having a large voltage swing, without generating audible distortion and without subjecting the drive stage tubes to excessively high voltages. The plate of a first drive tube is connected to the cathode of the second drive tube. A load impedance is connected from a B+ power supply terminal to the plate of the second drive tube. The grid of the second drive tube is driven by a signal responsive voltage divider network driven by the plate of the second drive tube.

Abstract: A horizontal junction-type field effect transistor having a saturated drain current to drain voltage characteristic and constituting an input transistor and a vertical junction-type field effect transistor having an unsaturated drain current to drain voltage characteristic and constituting an output transistor are connected in cascode fashion to compose a compound field effect transistor.This compound field effect transistor has a saturated characteristic, a high transconductance gm and a high breakdown voltage resembling those of a pentode vacuum tube.This compound field effect transistor is constructed in the form of monolithic integrated circuitry by the combined use of the dielectric isolation technique utilizing mesa groove and the pn-junction isolation technique.

Abstract: The present circuit comprises a simple variable capacitive coupling to ground for two outputs of a two-output amplifier wherein the frequency gain is either boosted or cut in accordance with the setting of a reactive coupling device. For high frequencies this may be capacitive and for low frequencies this may be inductive.