Precision Rectifier

EE JULY/AUGUST 1987 This precision rectifier oper- ates from an asymmetrical supply, handles input signals up to 3Vpp 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 Al is connected as a voltage ampli- fier (A0=1), A2 as an inverting amplifier (A0= -1). Opamp Az, transistor Ti and diode D2 ensure that the output voltage, U2, is identical to the positive excursions of the input voltage, Ul. When Ul is positive, the out- put of Ai 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 Di pro- tect the pnp input stage in A2 against negative voltages, which are effectively limited to -0.6 V. For negative excursions of the input signal, the function of A l, T2 and D2 is similar to the previously mentioned compo- PRECISION REi MI nents. The peak output voltage of the rectifier circuit is deter- mined mainly by the maximum output swi...