GB1093643A - Dielectric amplifier using non-linear capacitors - Google Patents

Abstract

1,093,643. Dielectric amplifiers. CESKOSLOVENSK‡ AKADEMIE V•D. April 8, 1965 [April 8, 1964], No. 14921/65. Heading H3B. A differential amplifier using non-linear capacitors consists of two parallel-connected branches, each containing a coupling capacitor, C v1 and C v2 , Fig. 1, a non-linear capacitor C N1 , C N2 , and a load impedance Z 1 , Z 2 , there being an alternating current source G connected across the branches, and the two inputs being connected respectively through low-pass filters F 1 , F 2 , to the junctions a, b, between a coupling capacitor and a non-linear capacitor; the output is taken from the junctions e, f, each between a non-linear capacitor and a load impedance, and a rectifier U is connected between these junctions. The A.C. from the source G appears at the points e, f as a pulsed voltage, the size and shape of which (Fig. 2b, 2d, not shown), depends upon the D.C. bias applied to the non-linear capacitors by the input signals at a, b. The output of the amplifier is the result of subtracting the two signals at e, f (Fig. 2e, not shown), and the unidirectional voltage produced by the rectifier U is then proportional to the difference between the two input signals. The rectifier U may be a diode, Fig. 1, a rectifying circuit (Fig. 3, not shown), or a transformer and a bridge rectifier (Fig. 4, not shown). Alternatively, the load impedances may be constituted by the two halves of a centre-tapped transformer primary (Fig. 5, not shown), of which the secondary drives a rectifier circuit. The sensitivity and stability of the amplifier is improved by including one positive voltage feedback circuit (Fig. 6, not shown), connected to the input filter F 2 . The input capacity of an input (e.g. input 1) is increased by a positive feedback circuit (Fig. 7, not shown), connected to the junction g of two capacitors C<SP>1</SP>V 1 and C<SP>11</SP>V 1 which together constitute one coupling capacity C V1 . The linearity of the amplifier may be increased by a negative current feedback circuit wherein the input terminal H (Fig. 7, not shown), is connected to a point h in the transformer secondary circuit instead of to the point d in the primary circuit.