Browse Prior Art Database

True/Complement Generator

IP.com Disclosure Number: IPCOM000061015D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Brosch, R: AUTHOR [+4]

Abstract

A fast true/complement (T/C) generator, based on a current switch, is described which guarantees an up-level priority at the in-phase and out-of-phase outputs. During switching, the complementary outputs of the T/C generator have a crossover point which is adjusted to be slightly below the up level of the output signal. If the T/C generator is used as an address phase splitter in conjunction with particular decoding concepts, the up-level priority prevents faulty addressing. Faulty addressing is eliminated by avoiding glitches at the output of the phase splitter and by simultaneously having the crossover point at phase splitter in-phase output IP and out-of-phase output OP adequately spaced from the operating threshold of a succeeding decoder.

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True/Complement Generator

A fast true/complement (T/C) generator, based on a current switch, is described which guarantees an up-level priority at the in-phase and out-of-phase outputs. During switching, the complementary outputs of the T/C generator have a crossover point which is adjusted to be slightly below the up level of the output signal. If the T/C generator is used as an address phase splitter in conjunction with particular decoding concepts, the up-level priority prevents faulty addressing. Faulty addressing is eliminated by avoiding glitches at the output of the phase splitter and by simultaneously having the crossover point at phase splitter in-phase output IP and out-of-phase output OP adequately spaced from the operating threshold of a succeeding decoder. The actual T/C generator consists of transistors T1 and T2 which, along with current source I1, form a current switch generating complementary output signals at outputs IP and OP through resistors R1 and R2. The up level of the output signals is by a diode voltage, generated by transistors T7 and T8, below the supply voltage VH (e.g.,
3.4 V). Transistors T7 and T8 are necessary for the optimum function of the up- level priority circuit. The up-level priority circuit consists of a cross-coupled current switch made up of transistors T3 and T4 and current source I2. The circuit characteristics can be influenced by changing the values of emitter resistors R3 and R4. Lower values of R3 and R4 lead to abrupt switching, while higher values lead to smooth and earlier switching. The crossover point of the current switch is controlled by outputs IP and OP through the bases of transistors T3 and T4. The current in transistors T3 and T4 determines the base potential of transistors T5 and T6 as a function of the voltage drop across resistors R5 and R8. The magnitude and waveform of the base potential control the up-level priority of the proposed circu...