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Low Saturation Voltage Transistor

IP.com Disclosure Number: IPCOM000088734D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Klink, E: AUTHOR [+4]

Abstract

The proposed circuit ensures that even with low-value load resistors a subsequent circuit stage is driven at a very low transistor saturation voltage.

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Low Saturation Voltage Transistor

The proposed circuit ensures that even with low-value load resistors a subsequent circuit stage is driven at a very low transistor saturation voltage.

In order to keep the internal collector bulk resistance low, transistors with two collector contacts 1 and 2 on the semiconductor surface are generally used on integrated semiconductor chips for driver circuits. For driver transistors, these contacts are always connected in parallel. Fig. 1 is a partial sectional view (without isolation) of the semiconductor structure of such a transistor. Above a highly doped buried layer 3, base 5, emitter 6 and, on both sides of the latter, the two collector contact regions 7 and 8 will be recognized in epitaxial layer 4. The respective internal collector bulk resistors are referred to as R1 and R2. In Fig. 2 transistor T1, described so far, is shown in a driver circuit within broken line frame A. T2 denotes the subsequent stage.

In contrast to the usual outer parallel connection, this proposal provides for collector contacts 1 and 2 to be split up. Collector contact 2 is directly connected to load resistor RL of transistor T1. Collector contact 1 serves to drive directly the next stage which includes T2. With T1 switched on, the internal saturation voltages of partial transistors T' and T'' are equal. The voltage drop on R2 does not affect the saturation voltage of T1. In this state, no current flows across resistor R1. On outer terminal 1 mere...