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The collector–emitter current can be viewed as being controlled by the base–emitter current (current control), or by the base–emitter voltage (voltage control). These views are related by the current–voltage relation of the base–emitter junction, which is the usual exponential current–voltage curve of a p–n junction (diode). [3]
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 ...
A bipolar junction transistor can be modeled as a dependent current source whose magnitude depends on the magnitude of the current fed into its controlling base terminal. An operational amplifier can be described as a voltage source dependent on the differential input voltage between its input terminals. [ 1 ]
A bipolar junction transistor (BJT) has terminals labeled base, collector and emitter. A small current at the base terminal, flowing between the base and the emitter, can control or switch a much larger current between the collector and emitter. A field-effect transistor (FET) has terminals labeled gate, source and drain. A voltage at the gate ...
The junction version known as the bipolar junction transistor (BJT), invented by Shockley in 1948. [10] Later the similar thyristor was proposed by William Shockley in 1950 and developed in 1956 by power engineers at General Electric (GE). The metal–oxide–semiconductor field-effect transistor (MOSFET) was also invented at Bell Labs.
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 collector potential of one of the inner BJT controls both the inner BJT's current by allowing the inner two BJTs to drop their emitter currents through the low residual voltage of the NMOSFET. As the MOSFET should not operate in reverse drain source polarity this restricts the current relations or emitter potentials that the circuit can ...
On a wafer, these two transistors are merged. A small voltage (around 1 volts) is supplied to the emitter of the current source transistor to control the current supplied to the inverter transistor. Transistors are used for current sources on integrated circuits because they are much smaller than resistors.