In: Electrical Engineering
Explain qualitatively the concept of superdiode. Draw a circuit that implements it and make a quantitative description
The precision rectifier is also known as a super diode, and this configuration is obtained with an operational amplifier in order to have a circuit behave like an ideal diode and rectifier, It is useful for high-precision signal processing.
In electronic circuits for many applications it is necessary to rectify signals that have low level voltages in the level of milli volts , But with a normal rectifier it requires minimum voltage of 0.3 volts fr germanium diode to operate in the circuit ,Hence this type of circuits is not useful for high precision signals processing.
The precision rectifier, also known as a super diode, is a configuration obtained with one or more operational amplifiers in order to have a circuit behave like an ideal diode and rectifier. Circuit designers have two standard methods for designing a precision rectifier. They can amplify the AC signal and then rectify it, or they can do both at once with a single operational amplifier.
The basic circuit of precision diode half wave rectifier or super diode is shown in following image...
when the input is positive supply, it is amplified by the operational amplifier and makes the diode on and a current will flow through the load. Due to the diode is on which makes a feed back in the circuit due to which the output voltage becomes same as input voltage with out any drop of diode.
When the input is negative supply the diode will becomes open circuit and no current will flows through the load and no output will present. Hence the circuit will works as half wave rectifier.
The following image shows the improved super diode rectifier circuit...
In this case when the input is positive the output of op-amp becomes negative which makes the diode D1 as off and D2 as on and the output voltage becomes zero.
When the input is negitive the op-amp output becomes positive because the input is applied toinverting terminal of op-amp and the diode D1 is on and D2 will be off and the output is like the input multiplied with gain of the opeartional amplifier.