|
Linear Regulator
| Linear regulator,
is basically a
voltage divider circuit, as shown in network Fig. 1 Where
the voltage output is Vo = Vi(R2/R1+R2). |
| Transistor in series actually works
like a variable resistor that adjust the resistance to maintain a
constant voltage on the output see Fig 2 |
| Passive linear regulators,
using zener as a constant voltage at the output Vo = Vz-Vbe, example
Vo = 12V-.6V = 11.4V (see Fig 2) |
| Active linear regulators are more precisely
and offer a externally well control and low ripple output and high
ripple rejection Vo = Vref ( R4/R5) see Fig 3 |
Advantages:
- Extremely low
ripple and noise
- Tight regulation
- Fast transient
response
- No RFI and EMI
Disadvantages:
- Efficiency Main
regulator 45% (depending of Vi)
- Large heat sink
required
- Lower power
supply density (Watts/cu.in.)
- Cost and
efficiency are the limitations for applications where high
current levels are required.
Example:
Click here to see a
Full schematic example of linear ±5V & +Variable Power
Supply
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August, 2002 |
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