GB1235473A - Amplifiers - Google Patents

Abstract

1,235,473. Transistor amplifiers. TEXAS INSTRUMENTS Ltd. 9 Aug., 1968 [21 June, 1967], No. 2855/71. Divided out of 1,235,472. Heading H3T. The transistors VT1, VT2 or VT3, of a distributed amplifier are connected through input transmission line branches IBL1, IBL2 or IBL3 to an input line which is decreased in characteristic impedance at each branch junction, and the transistor outputs are connected to an output line OPL by networks MNO which ensure that the outputs are added in phase. Each input branch is coupled to its transistor by a circuit MNI consisting of an inductance and a capacitance (Fig. 3, not shown) which matches the branch line Z 0 to the resistive part of the transistor input impedance. The input impedance of each transistor at the high frequencies of operation is regarded as being a series inductance (L 1 ) and a shunt resistance (R 1 ). The input line (and output line) is a strip line having a conductive layer separated by a dielectric layer from a ground plane, the width of the conductive layer which carries the input signal being reduced each time a branch line IBL1 &c. goes off. The output coupling circuits (Fig. 5, not shown) include an inductance, which couples the transistor output capacitance (C o ) and resistance (Ro) to the output line. The input coupling circuits may include a quarter wavelength section strip line connected to the L-C circuit (Fig. 4, not shown) and it is said that they could be Tchebycheff or Butterworth filters.