Itt Industries, Inc.

Mathew Neal

Friedrich Schmidtpott

Reiner Backes

Jochen Reimers

Between the source of operating voltage (U) and the zero point of the circuit there are provided four series arrangements (s1 . . . s4) of the controlled current paths of each time three insulated-gate field-effect transistors of the same conductivity type, of which the upper transistors (o1 . . . o4) as connected to the source of operating voltage, and the center transistors (m1 . . . m4) are of the depletion type and of identical geometry, while the lower transistors (u1 . . . u4) as connected to the zero point of the circuit, are of the enhancement type and likewise of identical geometry. The center transistors (m1, m3, m4) are connected as a resistors while the gate of the center transistor (m2) is connected to the point connecting the upper and the center transistor (o4, m4). The first input (e1) is connected to the gates of the upper transistors (o1, o3) and the second input (e2) to the gates of the upper transistors (o2, o4). The output of the inverter as formed by the series arrangements (s1 . . . s4) is the point connecting the respective lower and center transistors. The gates of the lower transistors (u2 . . . u4) are each connected to the output of the directly preceding inverter, while the gate of the lower transistor (u1) is connected to the output of its inverter, with the output of the fourth inverter being the output (a) of the comparator circuit.

Integrated comparator circuit

A first variant using conventional ratio-type two-phase design with nonoverlapping clock signals consists of a first inverter (I1), a complex gate (KG), a first transfer transistor (T1), a second inverter (I2), and a third inverter (I3) connected in series with respect to the signal flow. The complex gate (KG) consists of two NORed AND elements (U1, U2). The output of the second inverter (I2) is the count-up output (VA), and that of the third inverter (I3) is the count-down output (RA). The count-up output (VA) is coupled through a second transfer transistor (T3), controlled by the second clock signal (F2), to the first input of the first AND element (U1), whose second input is connected to the output of the first inverter (I1). The count-down output (RA) is coupled through a third transfer transistor (T2), controlled by the second clock signal (F2), to the first input of the second AND element (U2), whose second input is connected to the output of the NOR gate (NG) through a fourth transfer transistor (T 5), which is also controlled by the second clock signal (F2). One of the two inputs of the NOR gate is connected to the carry input (UE) in each stage. The carry input (UE) is connected to the carry output (UA) of the stage through a carry transfer transistor (UT). The carry input (UE) of the least significant stage is grounded. The second input of the NOR gate (NG) is connected to a stop line (S). The carry output (UA) is connected to a constant voltage (U) through a transfer transistor (T4) controlled by the countdown output (RA). In a second variant, the complex gate (KG) is omitted, so that the output of the first inverter (I1') is connected directly to the input of the second inverter (I2') through the first transfer transistor (T1'). The output of the NOR gate (NG') controls the gate of the second transfer transistor (T2'). Its first input is fed with the first clock signal (F1'), and its second input is connected to the carry input (UE). Those ends of the current paths of the second and third transfer transistors (T2', T3') not connected to the outputs are coupled to the input of the inverter (I1').

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Freiburg, Germany

Mathew Neal