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Hall Effect Device Voltage Divider

IP.com Disclosure Number: IPCOM000081293D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Braun, RJ: AUTHOR

Abstract

Differential amplifiers used with Hall generators often need a reduced voltage for the supply of the first differential amplifier stage. In Fig. 1, there is shown the conventional way of providing reduced voltage for the first differential amplifier transistor's T1 and T2 collectors, in order to keep transistor T4 out of saturation when driving transistor T5 fully "ON". A voltage drop is produced by transistor TD which is base-shorted to the collector and acts as a diode.

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Hall Effect Device Voltage Divider

Differential amplifiers used with Hall generators often need a reduced voltage for the supply of the first differential amplifier stage. In Fig. 1, there is shown the conventional way of providing reduced voltage for the first differential amplifier transistor's T1 and T2 collectors, in order to keep transistor T4 out of saturation when driving transistor T5 fully "ON". A voltage drop is produced by transistor TD which is base-shorted to the collector and acts as a diode.

In solving the problem of reducing the number of components that have to be put on a small integrated circuit (IC) chip, it was found that this voltage drop could be produced by a voltage tap electrode CT located on the vertical center line of the Hall cell, and connected to the collectors of transistors T1 and T2, as shown in Fig. 2. The voltage at CT is proportional to its location distance from the top main electrode. As long as the current drawn is small or constant, electrode CT has no adverse influence on the operation of the Hall cell.

In addition to eliminating the need for the transistor diode TD, the center-line electrode CT can be used as a voltage divider or reference voltage source in general. It will track the supply voltage or, if the Hall cell voltage is regulated, provide a stable predictable reference level.

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