This precision rectifier operates from an asymmetrical supply, handles input signals up to 3 Vpp and has a frequency range that extends from DC to about 2 kHz. Its amplification is unity, and depends mainly on the ratio R4/R3. Opamp A1 is connected as a voltage amplifier (Ao=l), Az as an inverting amplifier (Ao:-l). Opamp Az, transistor T1 and diode D2 ensure that the output voltage, U2, is identical to the positive excursions of the input voltage, U1. When U1 is positive, the out- put of A1 is held low at about 0.25 V, so that T2 is disabled and can not affect the rectified out- put signal. Components R2 and D1 protect the pnp input stage in Az against negative voltages, which are effectively limited to -0.6 V.
For negative excursions of the input signal, the function of A1, T2 and Dz is similar to the previously mentioned components. The peak output voltage . of the rectifier circuit is deter- ; mined mainly by the maximum output swing of the opamps and the voltage drop across the transistors plus D2: this amounts to about 3 V in all. When the circuit is not driven, it l consumes about lmA, and is therefore eminently suitable for building into portable, battery- operated equipment.
For negative excursions of the input signal, the function of A1, T2 and Dz is similar to the previously mentioned components. The peak output voltage . of the rectifier circuit is deter- ; mined mainly by the maximum output swing of the opamps and the voltage drop across the transistors plus D2: this amounts to about 3 V in all. When the circuit is not driven, it l consumes about lmA, and is therefore eminently suitable for building into portable, battery- operated equipment.
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