Transcript Precision Rectifier

Precision Rectifier
INTRODUCTION

The precision rectifier is also known as a super diode.

It is a configuration obtained with an operational
amplifier in order to have a circuit behaving like an
ideal diode and rectifier.

It can be useful for high-precision signal processing.
PRECISION RECTIFIER
BASIC CIRCUIT

The basic circuit implementing such a feature is
shown on the right, where RL can be any load.
BASIC CIRCUIT OF PRECISION RECTIFIER
CONT.,
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When the input voltage is negative, there is a
negative voltage on the diode, too, so it works like an
open circuit, there is no current in the load and the
output voltage is zero.
CONT.,
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When the input is positive, it is amplified by the
operational amplifier and it turns the diode on.

There is current in the load and, because of the
feedback, the output voltage is equal to the input.
CIRCUIT DIAGRAM
CONT.,

In fact the threshold of the super diode is not
actually zero, as it should be for an ideal one, but it
equals the threshold of the normal diode divided by
the gain of the operational amplifier, that is almost
zero.
SATURATION
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When the input becomes negative, the output of
the operational amplifier can easily become greater
than the voltage supplied to the op-amp, thus
causing saturation.
CONT.,
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If the input becomes positive again, the op-amp
has to get out of the saturation to amplify again.
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This change takes some time, and this greatly
reduces the frequency response of the circuit.
IMPROVED PRECISION RECTIFIER CIRCUIT
PRECISION HALF WAVE RECTIFIER
PRECISION FULL WAVE RECTIFIER
PEAK DETECTOR
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With little modifications basic precision rectifier can
be used also for detecting peak levels of signal.

In the following circuit a capacitor keeps the peak
voltage level of signal and switch can be used for
resetting detected level.
PEAK DETECTOR
THE END
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