06-02-2013, 12:54 PM
electronics fundamentals circuits, devices, and applications
[attachment=49824]
Introduction
A transistoris a semiconductor device that controls current between two terminals based on the current or voltage at a third terminal.
It is used for amplification or switching of electrical signals.
The basic structure of the bipolar junction transistor, BJT, determines its operating characteristics.
DC bias is important to the operation of transistors in terms of setting up proper currents and voltages in a transistor circuit.
Two important parameters are αDCand βDC
Bipolar junction transistors (BJTs)
The BJT is a transistor with three regions and two pn
junctions. The regions are named the emitter, the base, and
the collector and each is connected to a lead.
AC Input Resistance
The output voltage at the collector is 180 degrees out of phase with the input voltage at the base. Therefore, the CE amplifier is characterized by a phase inversion between the input and output. The inversion is sometimes indicated by a negative voltage gain.
The BJT as a switch
BJTs are used in switching applications when it is
necessary to provide current drive to a load.
In cutoff, the input voltage is too
small to forward-bias the
transistor. The output (collector)
voltage will be equal to VCC.
In switching applications, the transistor
is either in cutoff or in saturation.
When IIN is sufficient to saturate
the transistor, the transistor acts
like a closed switch. The output is
near 0 V.
[attachment=49824]
Introduction
A transistoris a semiconductor device that controls current between two terminals based on the current or voltage at a third terminal.
It is used for amplification or switching of electrical signals.
The basic structure of the bipolar junction transistor, BJT, determines its operating characteristics.
DC bias is important to the operation of transistors in terms of setting up proper currents and voltages in a transistor circuit.
Two important parameters are αDCand βDC
Bipolar junction transistors (BJTs)
The BJT is a transistor with three regions and two pn
junctions. The regions are named the emitter, the base, and
the collector and each is connected to a lead.
AC Input Resistance
The output voltage at the collector is 180 degrees out of phase with the input voltage at the base. Therefore, the CE amplifier is characterized by a phase inversion between the input and output. The inversion is sometimes indicated by a negative voltage gain.
The BJT as a switch
BJTs are used in switching applications when it is
necessary to provide current drive to a load.
In cutoff, the input voltage is too
small to forward-bias the
transistor. The output (collector)
voltage will be equal to VCC.
In switching applications, the transistor
is either in cutoff or in saturation.
When IIN is sufficient to saturate
the transistor, the transistor acts
like a closed switch. The output is
near 0 V.