Browse Prior Art Database

Voltage Range Enhancement for BIFET VLSI Circuits

IP.com Disclosure Number: IPCOM000036556D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Proch, TE: AUTHOR [+2]

Abstract

This article describes a circuit arrangement that allows voltages beyond the manufacturing process limitations to be generated by a bipolar field-effect transistor (BIFET) very large-scale integration (VLSI) chip.

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Voltage Range Enhancement for BIFET VLSI Circuits

This article describes a circuit arrangement that allows voltages beyond the manufacturing process limitations to be generated by a bipolar field-effect transistor (BIFET) very large-scale integration (VLSI) chip.

VLSI manufacturing processes are driving toward smaller (i.e., sub-micron) device dimensions to enhance performance (faster transitions and shorter propagation delays) and increase density. This inherently results in lower breakdown voltages across device terminals. Device terminal working voltages of 3 to 12 volts are typical for these processes. In real-world applications, it is often necessary to drive voltages higher than this off chip to communicate with older, standardized interfaces. The circuitry disclosed herein allows voltages beyond the process limitations to be generated by a BIFET VLSI chip.

The typical output stage of a driver (amplifier) would normally consist of the bipolar devices Q1, Q2, D1 and the Isource, as shown in

(Image Omitted)

Fig. 1. This "emitter-follower" configuration would provide unity voltage gain of the preamp output voltage and high current gain to the load. Essentially, the voltage at the output of the preamp is transferred to the load, but Q1 sources (Q2 sinks) directly from (to) the power rail whatever current is necessary to charge, discharge, and maintain this voltage across the load.

The limiting parameter for maximum output voltage of this circuit is the maximum collector-to-emitter voltage of the bipolar devices Q1 and Q2. This implies that the total voltage magnitude from +V and -V is approximately limited to the collector-emitter breakdown voltage of the bipolar devices in the chosen technology. Correspondingly, the driver output voltage is then limited to +V and - V minus the circuit losses. If this limitation were to be exceeded, the off (non- conducting) device Q1 or Q2 would break down when the complement device pulled the emitters past this threshold.

This problem is solved in the circuit of this disclosure with the introduction of "virtual power rails", called +V' and -V', as shown in Fig. 2. All output and preamp devices are connected to these virtual rails instead of the actual supply ...