also known as
are semiconductor devices that output
a constant and stable DC voltage at a specified level, despite
fluctuations in its input voltage or variations in its load.
Voltage regulator IC's have already become available in so many forms
and characteristics that they've virtually eliminated the need to build
voltage regulating circuits from discrete components.
that spurred the growth of the voltage regulator IC business include: 1)
ease with which zener diodes and balanced amplifiers can be built into
IC's; 2) improved IC heat dissipation capabilities; 3) advances in
overload protection techniques; and of course, 4) a high demand for
voltage regulators in almost all fields of the electronics industry,
especially in power supply applications.
selecting a voltage regulator include: 1) the desired output voltage
level and its regulation capability; 2) the output current capacity; 3)
the applicable input voltages; 4) conversion efficiency
(Pout/Pin); 5) the transient response time; 6) ease of use; and if
applicable, 7) the ability to step-down or step-up output voltages.
In switch-mode regulators, the switching frequency is also a
several types of voltage regulators, which may be classified in terms of
how they operate or what type of regulation they offer. The most
common regulator IC is the
A typical linear voltage regulator operates by forcing a fixed voltage
at the output through a voltage-controlled current source. It has
a feedback mechanism that continuously adjusts the current source output
based on the level of the output voltage. A drop in voltage would excite
the current source into delivering more current to the load to maintain
the output voltage. Thus, the capacity of this current source is
generally the limiting factor for the maximum load current that the
linear regulator can deliver while maintaining the required output
level. The amount of time needed
for the output to adjust to a change in the input or load is the
transient response time of the regulator.
The feedback loop used by
linear regulators need some form of compensation for stability. In
most linear regulator IC's, the required feedback loop compensation is
already built into the circuit, thereby requiring no external components
for this purpose. However, some regulator IC's, like the
low-dropout ones, do require that a capacitor be connected between the
output and ground to ensure stability. The main disadvantage of
linear regulators is their low efficiency, since they are constantly
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regulator is another type of regulator IC. It differs from the linear
regulator in the sense that it employs pulse width modulation (PWM) to
regulate its output. The output is controlled by current that is
switched at a fixed frequency ranging from a few Hz to a few kHz but
with varying duty cycle. The duty cycle of the pulses increase if
the output of the regulator needs to supply more load current to
maintain the output voltage and decreases if the output needs to be
reduced. Switching regulators are more efficient than linear
regulators because they only supply power when necessary.
Complexity, output ripples, and limited current capacity are the
disadvantages of switching regulators.
There is also a group of
regulator IC's known as
Low Drop-out (LDO) regulators.
The drop-out voltage is the minimum voltage across the regulator that's
required to maintain the output voltage at the correct level. The
lower the drop-out voltage, the less power is dissipated internally
within the regulator, the higher is the regulation efficiency. In LDO
regulators, the drop-out voltage is typically just about 0.6 V.
Even at maximum current, the drop-out voltage increases to just about
of regulator IC's include the following: 1) regulated power supplies; 2)
data conversion (ADC/DAC) circuits; 3) sensor and
4) DC-to-DC voltage converters; 5) measurement and instrumentation
systems; 6) motor control; and 7) battery charging.
ADC / DAC
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