offset-less rectifier

53 offset-Iess 4 MKH rectifier In an active rectifier the offset of the op-amp can cause the rectified output voltage to be incorrect. This is especially bad in appli- cations where precise measurement is essential. The offset can, of course, _ C2 22P D2 1N4148 7-64 be set to zero but this very correc- tion can cause temperature changes and ripple in the supply voltage which can cause even more prob- lems. The rectifier circuit shown here is C1 10k 2 "C1 R2 10k 7 R4 1N4148 rt1MkD1 220.CA6C3 331306 P1 6 ...12 V — R3 o lOk 2 63403 R6N 2501 not affected by offset, because the input and output of the op-amp are isolated from d.c. voltages by means of two capacitors (Cl and C3). If the circuit is imagined with- out these two capacitors it ap- pears as a normal active rectifier. The feedback for the positive half cycle is by means of Dl and R2, and feedback for the negative half cycle is via D2 and R3. R4 controls the d.c. setting of the op-amp. At the output we get the rectified a....