Precision Full Wave Rectifiers

Precision Full Wave Rectifiers

The Precision Full Wave Rectifiers circuits accept an ac signal at the input, inverts either the negative or the positive half, and delivers both the inverted and noninverted halves at the output, as shown in the Fig. 2.62.

Precision Full Wave Rectifiers

The operation of the positive full wave rectifier is expressed as

Precision Full Wave Rectifiers

and that of the negative rectifier as

Precision Full Wave Rectifiers

Looking at equations 1 and 2 we can say that Precision Full Wave Rectifiers circuits are precision absolute value circuits. Fig. 2.63 shows a full wave rectifier or absolute value circuit.

Precision Full Wave Rectifiers

CASE 1 : Vi > 0 : When Vi > 0, inverting side of Al will force its output to swing negative, thus forward biasing D1 and reverse biasing D2. Since no current flows through resistance R connected between Vn1 and Vp2, both are equipotential

Precision Full Wave Rectifiers

The Fig. 2.64 shows the equivalent circuit.

Precision Full Wave Rectifiers

From equivalent circuit, the output voltage can be given

Precision Full Wave Rectifiers

CASE 2 : Vi < 0 : When Vi < 0, negative, the output voltage of Al swings to positive, making diode D1 reverse biased and diode D2 forward biased.

The Fig. 2.65 shows the equivalent circuit.

Precision Full Wave Rectifiers

Let the output voltage of op-amp Al be V. Since the differential input to A2 is. zero, the inverting input terminal is also at voltage V, as shown in the Fig. 2.65.

Applying KCL at node ‘a’ we have

Precision Full Wave Rectifiers

Precision Full Wave Rectifiers

To find Vo in terms of V we concentrate on the equivalent circuit of A2, as shown in the Fig. 2.66.

Precision Full Wave Rectifiers

Substituting value of V in above equation

Precision Full Wave Rectifiers

Hence for Vi < 0 the output is positive. This is illustrated in Fig. 2.67.

Precision Full Wave Rectifiers

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