GB530620A - Improvements in or relating to thermionic valve circuit arrangements - Google Patents

Abstract

530,620. Valve amplifying circuits ; impedance networks. WHITE, E. L. C. May 10, 1939, No 13920. [Classes 40 (iii) and 40 (v)] An electrical network for evenly transmitting wide-band signals from a source, such as a pentode or triode valve, to a high impedance device, such as the grid circuit of a following valve, comprises a pair of branches in parallel, as shown in Fig. 2, one branch comprising a resistance aP in series with a paralleled resistance P and impedance α, the other branch comprising three series sections, a resistance Q shunted by an impedance #, a resistance bQ, and a resistance cQ shunted by an impedance c#, the multipliers a, b, c being real numbers such that a=b +e, and the impedances a, # being complex or purely imaginary and related by aP/α=bQ/#. If Q is not large compared with P, a resistance bQ/c is connected in parallel with the two branches, or is effectively incorporated in one of them. When applied as an inter-valve coupling, the impedance a may represent the anode de-coupling condenser 4 and the impedance c# the grid de-coupling condenser 10, whilst the impedance # may appear as a condenser 6 shunting a resistance 7 connected from anode of valve 1 to grid of valve 5, as shown in Fig. 1. In more complex arrangements α, #, and c # may each comprise networks of resistances and condensers. Fig. 6 shows a modified circuit which apart from the grid leak r is derivable by known transformations from the circuit of Fig. 1. The gain is independent of frequency provided that C2 R2=K2 S2 and R1+R2/R1=K1+K2/K1, and provided that the product K1r is large the range extends very closely to zero frequency. Specifications 456,450 and 527,188 are referred to.