GB913138A - Improvements in or relating to balanced electronic circuits - Google Patents

Abstract

913,138. Valve amplifying circuits; valve integrating and differentiating circuits. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Aug. 1, 1961 [Aug. 16, 1960], No. 28438/60. Class 40 (6). [Also in Group XXXVI] A balanced electronic circuit comprises a pair of input terminals connected by a pair of input components to the input electrodes of a balanced amplifier and a pair of feedback components connected between the amplifier output and the input electrodes to provide negative feedback, the impedance ratio between the input and feedback components connected to each input electrode being the same. Both input and feedback components may comprise resistors, so that the arrangement functions as an amplifier, or either input or feedback components may comprise capacitors, so that the arrangement functions respectively as a differentiator or integrator. In an embodiment the balanced amplifier comprises a first double valve V1 operating as a long-tailed pair and having a pentode V3 as common cathode impedance, R.C. coupled to a second double valve V2 also operating as a long-tailed pair. The second stage V2 feeds a double valve V4 acting as a pair of cathode followers, providing negative feedback over resistors R3<SP>1</SP>, R4<SP>1</SP> to the grids of the stage V1. Ouptut may be taken from the cathodes of the cathode followers V4 or, as shown, from potentiometer networks in the anode circuits, ganged switches S1/1, S1/2 allowing for different values of overall gain. The input to the amplifier is via series resistors R1<SP>1</SP>, R2<SP>1</SP>, a number of resistors being connected to each grid so that the arrangement may be used for summing a number of inputs. The resistors R1<SP>1</SP>, R2<SP>1</SP>, R3<SP>1</SP>, R4<SP>1</SP> are shunted by variable capacitors which allow for correction of the high-frequency response.