GB1078930A - Integrator network - Google Patents

Abstract

1,078,930. Field-effect transistor integrators. MOTOROLA Inc. Sept. 20, 1965 [Oct. 8, 1964], No. 39940/65. Heading H3T. [Also in Division G4] An integrating circuit useful as a sawtooth generator comprises two screen-electrode fieldeffect transistors in series, with a capacitor across the first, and the other having gate and source joined together, charging or discharging of the capacitor being effected by the difference between the pinch-off currents of the two transistors. In Fig. 1 (not shown) a variable resistor (16) in the source lead of the first transistor sets the potential of the junction point of the two transistors to be halfway between the supply potential points, so that the transistors pass equal currents and the capacitor (20) is charged to half the supply potential. Signals applied to the gate of the first transistor alter its pinch-off current and the capacitor charges or discharges under constant-current conditions, the potential across the capacitor representing the integral (positive or negative) of the applied signal. In Fig. 3, a sawtooth generator comprises a circuit as in Fig. 1 but with the input applied to the source of the first transistor 14. During the negative portions of a square wave applied at 46, transistors 44 and 48 are cut off and capacitor 20 charges linearly. When the square wave goes positive, transistor 48 discharges the capacitor and transistor 44 short-circuits resistor 42 to equalize the pinchoff currents of the field-effect transistors and restore the static condition of Fig. 1.