GB981149A - An improved integrating circuit - Google Patents

Abstract

981,149. Integrating circuits. ATOMENERGIKOMMISSIONEN. May 4, 1961 [May 5, 1960], No. 16123/61. Heading G4G. An integrating circuit comprises a D.C. amplifier, a main capacitor connected between the input and output of the amplifier and an auxiliary capacitor arranged so that it may be connected alternatively either between the input of the amplifier and a point on a voltage divider connected between the output of the amplifier and earth or as a member of a circuit designed to change the charge of the auxiliary capacitor, so that the voltage output of the amplifier may be scaled by a given factor. One circuit embodiment (Fig. 3) may be used for either up or down scaling, and allows the auxiliary capacitor to be charged from the initial potential across the amplifier itself. During the initital operation of the integrating circuit the auxiliary capacitor C 2 is connected as shown in Fig. 3, so that it is charged to a voltage e u . For upscaling, the switch 4 is opened, and the switch 10 is adjusted to connect the capacitor C 2 to the point 9. Then, since total charge remains constant Cu (C 1 + C 2 ) = ae u C 1 + kae u C 2 where k = R 2 /R 1 +R 2 and a is the scaling factor. Thus a = C 1 /C 2 + 1 / C 1 /C 2 +K, representing an upscaling since k < 1. When the operation is finished the switches 10 and 11 are changed so that C 2 is connected to earth (through the resistor R 3 ) and to the output point 3 so that the capacitors become charged to a value in accordance with the output voltage of the amplifier after rescaling, i.e. aE. If the capacitor C 2 is finally connected across the amplifier 1 again and the switch 4 is closed, the operation of the integrating circuit can continue. (The switch 4 could be kept closed throughout the operation, but with loss of accuracy). Downscaling may be produced by altering the switching sequence. The switches may be automatically operated by using circuits designed to operate appropriate relays when the output voltage from the integrator reaches a limit value. A more simple circuit suitable only for upscaling is also described, using a battery for charging the ausiliary capacitor (Fig. 2 not shown).