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Measurement of Conductivity Modulation in Base Region of a Transistor

IP.com Disclosure Number: IPCOM000081781D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Dunkel, WE: AUTHOR [+2]

Abstract

Conductivity modulation in a transistor is the effect that at high-injection levels of emitter current, the resistance in the base region measured parallel to the junction decreases.

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Measurement of Conductivity Modulation in Base Region of a Transistor

Conductivity modulation in a transistor is the effect that at high-injection levels of emitter current, the resistance in the base region measured parallel to the junction decreases.

The drawing shows an apparatus for measuring this effect in a transistor 2. Transistor 2 has circular base and emitter contacts, and it has two base terminals 3 and 4 and associated internal base resistances represented schematically as resistors 5 and 6. An oscillator 7 is connected to apply a selected frequency to terminal 3 and a cathode-ray tube (CRT) oscilloscope 8 is connected to show the voltage at terminal 3. A resistor 9 is connected between base terminal 4 and ground, to provide a measure of a bias current that is applied to the base-emitter junction from a source that is not shown in the drawing.

Band reject filters 10 and 11 are connected in the collector and emitter circuits of transistor 2, so that these branches present a very high impedance to the signal of oscillator 7. Thus, the signal at CRT 8 indicates the values of internal base resistances 4 and 5 for a particular value of bias current and a particular frequency of oscillator 7.

Transistor 2 is then disconnected from the circuit of the drawing and is connected with both junctions reverse biased, so that it operates as a field-effect transistor (FET). From a theoretical understanding of FET's, it is possible to calculate separately the resistan...