Precision Full Wave Rectifier 596h2k

PRECISION FULL WAVE RECTIFIER In PFWR, for both the half cycles output is produced & in one direction only. The diagram below shows an inverting type of Precision FWR with positive output. It is also called as absolute value circuit because output signal swing is only in positive direction. So we get absolute value of input signal.

In positive half cycle of applied ac input signal, output of first op-amp (A1) is Negative. Therefore diode D2 is forward biased & diode D1 is reverse biased. Here op-amp A1 works as an inverting amplifier with gain =(-R/R)=-1 Therefore output of op-amp A1 is ,V=(-1) Vin=-Vin Op-amp A2 works as an inverting adder. The two inputs to the op-amp A2 are voltage V (output of A1) and input voltage Vin. Thus output of op-amp A2i.e. Output voltage is given as ∴Vo=-[R/R Vin+R/(R⁄2) V ] ∴Vo=-[Vin+2V] Substituting V=-V_in ∴Vo=Vin In negative half cycle of applied ac input signal, output of first op-amp (A1) is positive. Therefore diode D2 is reversed biased & diode D1 is forward biased. Due to virtual ground concept output of op-amp A1is zero. (∴V=0) Thus output of op-amp A2, i.e. Output voltage is given as ∴Vo=-[R/R Vin+R/(R⁄2) V ] ∴Vo=-[R/R Vin+R/(R⁄2) (0) ] But in negative half cycle input magnitude is negative therefore we get, ∴Vo=-[R/R (-Vin ) ] ∴Vo=Vin Thus in both the half cycles output is positive & in one direction & also have same magnitude. Thus it is also called as non-saturating type of PFWR because op-amp A1 is not going in saturation. The transfer characteristics and input-output waveforms of PFWR are shown below,

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Precision Full Wave Rectifier Circuit Srihari Rao

The use of Operational amplifiers can improve the performance of a wide variety of signal processing circuits. In rectifier circuits, the voltage drop that occurs with an ordinary semiconductor rectifier can be eliminated to give precision rectification. The below shown circuit is the precision full wave rectifier. It consists of following sections: 1. Precision half-wave rectifier 2. Inverting summing amplifier The input voltage Vin is applied to one terminal of the summing amplifier along with resistor R3 and to the input of the precision rectifier. The output of precision rectifier is applied to another terminal of summing amplifier. The precision half-wave rectifier circuit uses an inverting amplifier configuration. Related Products: Bridge Rectifier | Current Regulator

When the input signal Vin is positive, Op-Amp output terminal is negative, Diode D1 is reverse biased and D2 Diode is forward biased, the circuit is Vb = -(R2/R1) * Vin In the circuit, R1 and R2 have been chosen such that R2 = 2R1. So the voltage at Vb = -2Vin. Thus during the positive half cycle of the rectified voltage Vb is applied to terminal B of the inverting summing amplifier is -2Vin.

The voltage at terminal A is Va = +Vin. The output from the summing circuit with R3=R4=R5 is Vo = – (Va+Vb). Hence Vo = -(Vin – 2Vin) = +Vin. So during the negative half cycle of the input, the Op-Amp output terminal goes positive, causing D2 to be reverse biased. Without D1 in the circuit, the Op-Amp output would be saturated in the positive direction. However, the positive voltage at the Op-Amp output forward biases the D1. This tends to pull the Op-Amp inverting terminal in a positive direction. But, such a move would cause the Op-Amp output to go negative. So, the output settles at the voltage close to ground level. So to be clear, the negative half-cycle is clipped off. That is Vb=0 and Va = -Vin. Totally the Vo will be Vo = -(-Vin+0) = +Vin. It is seen that the output is a full wave rectified version of the input voltage. A Precision fullwave rectifier is also known as absolute value circuit. This means the circuit output is the absolute value of the input voltage regardless of polarity. If you any doubt about the circuit please drop it in comments we will respond you.; v