I have a book entitled "The Transistor" by E.Wolfendale from 1963 which includes a passage on Early Effect. The description is based on the emitter being connected to the input of a transmission line with branches running to the collector and base.
Apparently this is still available see The transistor: an introduction to its applications - E. Wolfendale - Google Books. but still protected by copyright.
Apparently this is still available see The transistor: an introduction to its applications - E. Wolfendale - Google Books. but still protected by copyright.
I don't know if it is available anywhere else, but if the copyright is good still, don't post more than an excerpt (fair use).
-Chris
-Chris
Wolfendale's transmission line argument which I have shortened, says when the voltage applied at the collector decreases this results in an increase in the width of the base which equates to an increase in the length of the transmission line giving an increased loss.
Further since the transmission line is terminated by a short circuit this is accompanied by an increased input impedance.
By further analysis, for a given increase in emitter voltage the increase in emitter current will be less than expected by virtue of the increased input impedance - while on the other hand the collector current will be less due to the increased loss in the transmission line.
If the collector voltage is increased the process is reversed.
The losses in Wolfendale's emitter transmission line is shown as a chain of series resistances some with shunt capacitance and resistance combination connecting to the base progressively along the junctions in the series resistor chain.
Also at the transmission line input there is a capacitance between the emitter and base which is dependent on the width of the emitter depletion layer.
Both emitter and base transmission networks terminate at a common point ahead of the Early feedback generator situated at the collector -so there are two possible main internal feedback paths with cross coupled elements of shunt.
Wolfendale's summary is the (Early) generator voltage is a small fraction of the voltage appearing across the collector junction. Diagramaticly the generator is depicted in terms of current with parallel current dependent capacitance.
Further since the transmission line is terminated by a short circuit this is accompanied by an increased input impedance.
By further analysis, for a given increase in emitter voltage the increase in emitter current will be less than expected by virtue of the increased input impedance - while on the other hand the collector current will be less due to the increased loss in the transmission line.
If the collector voltage is increased the process is reversed.
The losses in Wolfendale's emitter transmission line is shown as a chain of series resistances some with shunt capacitance and resistance combination connecting to the base progressively along the junctions in the series resistor chain.
Also at the transmission line input there is a capacitance between the emitter and base which is dependent on the width of the emitter depletion layer.
Both emitter and base transmission networks terminate at a common point ahead of the Early feedback generator situated at the collector -so there are two possible main internal feedback paths with cross coupled elements of shunt.
Wolfendale's summary is the (Early) generator voltage is a small fraction of the voltage appearing across the collector junction. Diagramaticly the generator is depicted in terms of current with parallel current dependent capacitance.
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