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A small change to the input current results in much larger change in the output current supplied to the output load. One aspect of buffer action is transformation of impedances. For example, the Thévenin resistance of a combination of a voltage follower driven by a voltage source with high Thévenin resistance is reduced to only the output ...
A schematic diagram of the Ebers-Moll models of a PNP BJT. The base, collector and emitter currents are I B, I C and I E, the common-base forward and reverse current gains are α F and α R, and the collector and emitter diode currents are I CD and I ED. Date: 4 August 2010, 05:26 (UTC) Source: Ebers-Moll_Model_PNP.PNG; Author
A diode-connected transistor is made by connecting the base and collector of a BJT; the drain and source of a JFET [1] the gate and drain of a MOSFET; Diode-connected transistors are used in current mirrors to provide a voltage drop that tracks that of the other transistor as temperature changes. [2] They also have very low reverse leakage ...
The remainder of the electrons recombine with holes, the majority carriers in the base, making a current through the base connection to form the base current, I B. As shown in the diagram, the emitter current, I E, is the total transistor current, which is the sum of the other terminal currents, (i.e. I E = I B + I C).
In a diode model two diodes are connected back-to-back to make a PNP or NPN bipolar junction transistor (BJT) equivalent. This model is theoretical and qualitative. This model is theoretical and qualitative.
Full hybrid-pi model. The full model introduces the virtual terminal, B′, so that the base spreading resistance, r bb, (the bulk resistance between the base contact and the active region of the base under the emitter) and r b′e (representing the base current required to make up for recombination of minority carriers in the base region) can be represented separately.
For a current buffer, if the current is transferred unchanged (the current gain β i is 1), the amplifier is again a unity gain buffer; this time known as a current follower because the output current follows or tracks the input current. As an example, consider a Norton source (current I A, parallel resistance R A) driving a resistor load R L.
Reduction of the output impedance of the signal source connected to the base (e.g., by using an emitter follower or some other voltage follower). Using a cascode configuration, which inserts a low input impedance current buffer (e.g. a common base amplifier) between the transistor's collector and the load. This configuration holds the ...