Transistor Biasing Circuits & Thermal Stability | Analog and Digital Electronics - Electrical Engineering (EE) PDF Download

 Page 1


Transistor Biasing Circuits and Thermal Stability.
Contents:
Ø Introduction
Ø The Operating Point and Biasing Stability
Ø Fixed-Bias Circuits
Ø Fixed Bias with Emitter Resistance
Ø V oltage-Divider Bias Circuits
1 Nasim Zafar
Page 2


Transistor Biasing Circuits and Thermal Stability.
Contents:
Ø Introduction
Ø The Operating Point and Biasing Stability
Ø Fixed-Bias Circuits
Ø Fixed Bias with Emitter Resistance
Ø V oltage-Divider Bias Circuits
1 Nasim Zafar
Objectives:
Ø Discuss the concept of dc biasing of a transistor for the linear
operation in the active region.
Ø Establish an operating point Q in this active region to provide
appropriate potentials and currents.
Ø Analyze the voltage-divider bias, base bias, and collector-
feedback bias circuits.
Ø Establish a criterion for comparing the stability of different
biasing circuits.
2 Nasim Zafar
Page 3


Transistor Biasing Circuits and Thermal Stability.
Contents:
Ø Introduction
Ø The Operating Point and Biasing Stability
Ø Fixed-Bias Circuits
Ø Fixed Bias with Emitter Resistance
Ø V oltage-Divider Bias Circuits
1 Nasim Zafar
Objectives:
Ø Discuss the concept of dc biasing of a transistor for the linear
operation in the active region.
Ø Establish an operating point Q in this active region to provide
appropriate potentials and currents.
Ø Analyze the voltage-divider bias, base bias, and collector-
feedback bias circuits.
Ø Establish a criterion for comparing the stability of different
biasing circuits.
2 Nasim Zafar
Transistor Biasing Circuits:
an Introduction
Ø Biasing refers to the establishment of suitable dc values of different currents
and voltages of a given transistor.
Ø Through proper biasing, a desired DC operating point or quiescent point;
Q-Point of the transistor amplifier, in the active region (linear region) of the
characteristics is obtained.
Ø The goal of amplification, in most cases, is to increase the amplitude of an ac
signal without  distortion or clipping the wave form.
3 Nasim Zafar
Page 4


Transistor Biasing Circuits and Thermal Stability.
Contents:
Ø Introduction
Ø The Operating Point and Biasing Stability
Ø Fixed-Bias Circuits
Ø Fixed Bias with Emitter Resistance
Ø V oltage-Divider Bias Circuits
1 Nasim Zafar
Objectives:
Ø Discuss the concept of dc biasing of a transistor for the linear
operation in the active region.
Ø Establish an operating point Q in this active region to provide
appropriate potentials and currents.
Ø Analyze the voltage-divider bias, base bias, and collector-
feedback bias circuits.
Ø Establish a criterion for comparing the stability of different
biasing circuits.
2 Nasim Zafar
Transistor Biasing Circuits:
an Introduction
Ø Biasing refers to the establishment of suitable dc values of different currents
and voltages of a given transistor.
Ø Through proper biasing, a desired DC operating point or quiescent point;
Q-Point of the transistor amplifier, in the active region (linear region) of the
characteristics is obtained.
Ø The goal of amplification, in most cases, is to increase the amplitude of an ac
signal without  distortion or clipping the wave form.
3 Nasim Zafar
Transistor Biasing Circuits:
an Introduction
Ø The selection of a proper DC operating point or quiescent point, generally
depends on the following factors:
(a)  The amplitude of the ac signal to be handled by the amplifier and
distortion level in signal. Applying large ac voltages to the base would
result in driving the collector current into saturation or cutoff  regions
resulting in a distorted or clipped wave form.
(b)  The load to which the amplifier is to work for a corresponding supply
voltage.
4 Nasim Zafar
Page 5


Transistor Biasing Circuits and Thermal Stability.
Contents:
Ø Introduction
Ø The Operating Point and Biasing Stability
Ø Fixed-Bias Circuits
Ø Fixed Bias with Emitter Resistance
Ø V oltage-Divider Bias Circuits
1 Nasim Zafar
Objectives:
Ø Discuss the concept of dc biasing of a transistor for the linear
operation in the active region.
Ø Establish an operating point Q in this active region to provide
appropriate potentials and currents.
Ø Analyze the voltage-divider bias, base bias, and collector-
feedback bias circuits.
Ø Establish a criterion for comparing the stability of different
biasing circuits.
2 Nasim Zafar
Transistor Biasing Circuits:
an Introduction
Ø Biasing refers to the establishment of suitable dc values of different currents
and voltages of a given transistor.
Ø Through proper biasing, a desired DC operating point or quiescent point;
Q-Point of the transistor amplifier, in the active region (linear region) of the
characteristics is obtained.
Ø The goal of amplification, in most cases, is to increase the amplitude of an ac
signal without  distortion or clipping the wave form.
3 Nasim Zafar
Transistor Biasing Circuits:
an Introduction
Ø The selection of a proper DC operating point or quiescent point, generally
depends on the following factors:
(a)  The amplitude of the ac signal to be handled by the amplifier and
distortion level in signal. Applying large ac voltages to the base would
result in driving the collector current into saturation or cutoff  regions
resulting in a distorted or clipped wave form.
(b)  The load to which the amplifier is to work for a corresponding supply
voltage.
4 Nasim Zafar
The DC Operating Point:
Biasing and Stability
Ø The goal of amplification, in most cases, is to increase the amplitude
of an ac signal without distortion or clipping the wave form.
5 Nasim Zafar