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High-Speed, Non-Saturating Logic Block

IP.com Disclosure Number: IPCOM000098002D
Original Publication Date: 1961-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Trampel, KM: AUTHOR

Abstract

A Zener diode Z is operated in its reverse characteristic to obtain high speed and non-saturation of the logic block. The NPN transistor block includes a logic circuit having a plurality of diode networks D1 for coupling the input voltage levels to Z, a transistor T1 connected at its emitter electrode in common base configuration to Z, clamping circuit diodes D2 and D3, and output transistor T2 connected as an emitter follower.

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High-Speed, Non-Saturating Logic Block

A Zener diode Z is operated in its reverse characteristic to obtain high speed and non-saturation of the logic block. The NPN transistor block includes a logic circuit having a plurality of diode networks D1 for coupling the input voltage levels to Z, a transistor T1 connected at its emitter electrode in common base configuration to Z, clamping circuit diodes D2 and D3, and output transistor T2 connected as an emitter follower.

The logic is performed by the networks D1. When any input voltage level is down, i.e., at -V5, the node at C is down, causing Z to conduct heavily. This permits current I1 to flow through the emitter of T1. This current is limited by resistor R2 and causes a voltage drop across resistor R3. The voltage at the T1 collector is clamped by D3 at +V3, enabling T2 to provide an output voltage level at approximately +V3 volts.

If all the input voltage levels to the diodes D1 are up, i.e., at -V6, node C is up at a voltage level less than that of the breakdown voltage level VZ of the Z. The current flowing through the T1 emitter is negligible, and the collector is clamped by diode D2 at +V2 volts. This enables T2 to provide an output level at approximately +V2 volts.

Extremely fast speed is achieved by operating Z in its reverse characteristic. As shown in the I-V curve, Z and the T1 emitter current are switched between the points A and B, i.e., from an appreciably high current condition to an extremely low c...