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# Circuit With Step Function Characteristic

IP.com Disclosure Number: IPCOM000078306D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 25K

IBM

## Related People

Keller, G: AUTHOR [+3]

## Abstract

In many instances, for example, when reading associative-storage arrays or when discharging a capacity, differently high currents occur which have to be accommodated by the associated current sink. With known current switch circuits, it would be necessary in all these instances to maintain the maximum current also in the quiescent state.

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Circuit With Step Function Characteristic

In many instances, for example, when reading associative-storage arrays or when discharging a capacity, differently high currents occur which have to be accommodated by the associated current sink. With known current switch circuits, it would be necessary in all these instances to maintain the maximum current also in the quiescent state.

In the drawing, circuitry 1 represents such a circuit supplying differently high currents. If the reference voltage VR on the base of T2 is more positive than voltages V1 to Vm, T2 is conductive, so that current flows from +Vc, through R, T2 and T3 to ground, with T being zero. Due to the voltage drop over R, the potential at point A is lowered and fed back to the base of T3, so that T3 is reverse-biased. The resulting current is thus kept very low and is adjustable as a function of the magnitude of resistor R. T4, used for level adaptation, acts as an emitter-follower for the voltage fed back from point A.

If, on the other hand, V1 and/or Vn increases beyond VR, T2 is cut off and T1 and/or Tn become conductive. With T2 being switched off, the potential at point A assumes a relatively positive value which is fed back to the base of T3. Then T3 becomes more strongly conductive, permitting the high-current flow I to ground. The maximum permissible current I can be adjusted by resistor R. This leads to a circuit which, although having only a low-power dissipation for V1 ... Vn < VR, can deri...