Browse Prior Art Database

On Chip Constant Current Compensator

IP.com Disclosure Number: IPCOM000086047D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Chu, WM: AUTHOR

Abstract

This is a circuit for holding power and (to a lesser extent) delays within a circuit on a chip at a near constant level, thereby compensating for inherent process and operating condition variations.

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On Chip Constant Current Compensator

This is a circuit for holding power and (to a lesser extent) delays within a circuit on a chip at a near constant level, thereby compensating for inherent process and operating condition variations.

It is known that due to process parameter variation and operating voltage and temperature variation, the circuit current (and hence power and delay) in field- effect transistor (FET) chips varies widely from chip-to-chip. The described circuit generates a load gate voltage internally and automatically adjusts itself such that the circuit current in every chip is nearly identical.

As illustrated in Fig. 1, the circuit utilizes a precision resistor R1 to measure the circuit current by translating it into a voltage. A voltage divider consisting of resistors R2 and R3 is used to generate a reference voltage (Vref). These two voltages, Vref and the voltage obtained through R1 (VM) are fed to a voltage comparator. The output of the voltage comparator (VC) is applied to a load gate voltage (VLG) generator which provides the load gate voltage (VLG). This load gate voltage (VLG) is then applied to the load transistor in the typical logic circuit or other circuit to be compensated, as illustrated in Fig. 2.

With continued reference to Fig. 1, it is seen that the load gate voltage is also applied to the gate of transistor T3. Transistor T3 and T4 are two series connected FET devices for sensing the circuit current in the chip. If the circuit current (IL) in the chip is lower than the designed nominal value, then the voltage VM will rise above the voltage Vref. The output of the voltage comparator will cause the VLG generator to raise its output, which in...