IE32840L - Coupling arrangement for amplifiers - Google Patents

Abstract

1,206,675. Circuit assemblies. STANDARD TELEPHONES & CABLES Ltd. 29 Feb., 1968, No. 9823/68. Heading H1R. [Also in Division H3] The couplings between the transistors (e.g. Tr1 and Tr2, Fig. 1, not shown) of a u.h.f. or v.h.f. amplifier are in the form of 1/4 wavelength or less low-Q strip transmission lines (e.g. TL2) having a characteristic impedance of less than 50 ohms, for maximum power transfer. The circuit is a power amplifier for a transmitter, the output circuit and aerial being driven by a parallel pair of transistors (Tr3, Tr4). The D.C. bias for all the transistors is supplied by associated inductances (L1-L8). The low-Q strip transmission line couplings for the amplifier are made by etching away portions of a copper layer on an insulating plate (Fig. 3, not shown) to leave tracks (TL2, TL4), and on a second plate (Fig. 4, not shown) to leave tracks (TL1 and TL3). Both plates 3, 7, Fig. 6, have metallized layers on their reverse faces and are overlaid by respective insulating plates 6, 8 having a layer on one face only and arranged with the non-metallized face contacting the tracks (TL1-TL4). A final copper clad plate 9 carries the remaining circuitry, the inter-connections and some of the inductances (L1-L4, Fig. 5, not shown) being formed from the copper layer, and the other inductances (L5-L8) and the capacitance being separate units wired to the plate. The transistors are mounted in clips 1 attached to the lower plate, and their electrodes connected through appropriate holes in the plates. [GB1206675A]