Browse Prior Art Database

Automatic Beta Plotter

IP.com Disclosure Number: IPCOM000094478D
Original Publication Date: 1965-Feb-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Hilsenrath, F: AUTHOR [+2]

Abstract

This circuit provides direct reading of the Beta of the transistor under test. The circuit compares emitter current to base current rather than measuring the base current of a transistor under test. The former is directly proportional to the Beta factor. The latter is the reciprocal of the Beta factor. The circuit is able to drive an X-Y plotter which can be adapted to plot the Beta factor versus the current for the transistor under test.

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Automatic Beta Plotter

This circuit provides direct reading of the Beta of the transistor under test. The circuit compares emitter current to base current rather than measuring the base current of a transistor under test. The former is directly proportional to the Beta factor. The latter is the reciprocal of the Beta factor. The circuit is able to drive an X-Y plotter which can be adapted to plot the Beta factor versus the current for the transistor under test.

Transistor 10 to be tested has collector, base and emitter leads. The collector is connected to supply voltage Ecc. The base is suitably biased by variable resistor Rb and bias voltage Ebb. The voltage of the base of transistor 10 is compared with reference voltage Eb by operational amplifier 20. The output of amplifier 20 and the emitter of transistor 10 are connected to base and collector electrodes, respectively, of control transistor 30. The emitter of transistor 30 is connected through load resistor Re to a reference potential, typically, ground. Operational amplifier 40, including a variable resistor Rf, is connected across Re and a suitable dropping resistor R1. Resistor Rf which is identical to Rb, is ganged to Rb of the transistor under test.

Transistor 30 is chosen to have an alpha near unity. The input impedance to amplifiers 20 and 40 is very high. Based on these criteria, the emitter current of transistor 10 equals the emitter current of transistor 30. The output voltage appearing at amplifier...