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# Logic Circuit With Diode As Part of Load Resistance

IP.com Disclosure Number: IPCOM000041564D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 26K

IBM

## Abstract

An improvement in performance, as measured by speed power product, is achieved over conventional DTL (diode-transistor logic) circuits by the addition of a Schottky diode as part of the circuit load. In the NAND circuit shown in the figure, high barrier Schottky diode D1 is added to an otherwise conventional DTL circuit. The addition of D1 improves the circuit because its voltage drop changes non-linearly, as the current changes through D1, dynamically changing the effective value of the collector resistor during the switching cycle. This allows a smaller value of RC to be used than would otherwise be needed for the same power levels. The power consumed by the circuit can be increased for a particular cell on a masterslice by shorting D1. By doing this, the speed of the cells on a masterslice can be selectively increased.

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Logic Circuit With Diode As Part of Load Resistance

An improvement in performance, as measured by speed power product, is achieved over conventional DTL (diode-transistor logic) circuits by the addition of a Schottky diode as part of the circuit load. In the NAND circuit shown in the figure, high barrier Schottky diode D1 is added to an otherwise conventional DTL circuit. The addition of D1 improves the circuit because its voltage drop changes non-linearly, as the current changes through D1, dynamically changing the effective value of the collector resistor during the switching cycle. This allows a smaller value of RC to be used than would otherwise be needed for the same power levels. The power consumed by the circuit can be increased for a particular cell on a masterslice by shorting D1. By doing this, the speed of the cells on a masterslice can be selectively increased. Diode D2 is an antisaturation clamp for the transistor. It must be a high barrier Schottky diode. Diodes D3-D5 perform the AND logic function. As many diodes as are desired can be connected in a similar manner. The three shown here are a typical implementation. Resistors RB and RC form the bias network for the transistor. The values are determined by the power consumption desired by the circuit.

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