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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 ...
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).
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 ...
Figure 4: Typical BJT constant current source with negative feedback. In this bipolar junction transistor (BJT) implementation (Figure 4) of the general idea above, a Zener voltage stabilizer (R1 and DZ1) drives an emitter follower (Q1) loaded by a constant emitter resistor (R2) sensing the load current. The external (floating) load of this ...
In a circuit with a three terminal device, such as a transistor, the current–voltage curve of the collector-emitter current depends on the base current. This is depicted on graphs by a series of (I C –V CE) curves at different base currents. A load line drawn on this graph shows how the base current will affect the operating point of the ...
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.
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 ...
A translinear circuit is a circuit that carries out its function using the translinear principle. These are current-mode circuits that can be made using transistors that obey an exponential current-voltage characteristic—this includes bipolar junction transistors (BJTs) and CMOS transistors in weak inversion.