GB527626A - Radio amplifiers and the like - Google Patents

Abstract

527,626. Impedance networks; valve circuits. MAGUIRE, I. L. Nov. 21, 1938, No. 33835. Convention date, Nov. 26, 1937. [Classes 40 (iii) and 40 (v)] Wide-band amplifiers are rid of distortion, due to inter-electrode feedback, by the use of input, intervalve, and output networks of constant impedance and comprising resistances which reduce the energy feed-back. Each network may comprise a resistance R and condenser C, Fig. 8 (and Fig. 3, not shown) in parallel with resistances r<SP>1</SP>, r<SP>2</SP> and inductances l<SP>1</SP>, l<SP>2</SP> where (r<SP>1</SP> + r<SP>2</SP>)= R, (l<SP>1</SP> + l<SP>2</SP>) = CR2, and r<SP>1</SP>/r<SP>2</SP> = l<SP>1</SP>/l<SP>2</SP>. Then the impedance between the output terminals A, D is a constant resistance equal to R, and that between the output terminals B, D is a constant real fraction of R. The resistance r<SP>2</SP> may be the grid leak resistance as shown. Other forms of network are shown in Figs: 5, 6, 7 where the condensers C<SP>6</SP>, C<SP>7</SP>, C<SP>1</SP>, C<SP>2</SP>, C<SP>8</SP> are blocking condensers to prevent d.c. coupling ; and the inductances l<SP>1</SP>, l<SP>2</SP> may be interchanged with the capacitances C, as in the circuit 5, Fig. 8 (and Fig. 4, not shown), the circuits 4, 5 being associated with the grids and the anodes respectively of the valves. Valve circuits embodying these networks as grid-leaks (as at 4, Fig. 8) or anode loads (as at 5) are illustrated in Figs. 5a, 9, (not shown) and push-pull valve circuits of the same kind in Figs. 10, 11 (not shown), while Figs, 12, 13, 14 (not shown) illustrate the manner in which the invention reduces the undesired feedback. Mutual inductance may be used instead of self-inductances.