Rectifier tracks positive and negative peaks

摘要

Signals ranging from music to complex control-system waveforms may contain unequal positive and negative peak amplitudes. An "envelope-follower" circuit can track unequal peaks, but the ability to select a desired peak can enhance the circuit's performance (Reference 1). The circuit in Figure 1 applies a new twist to a classic absolute-value circuit. Applying an input signal to R{sub}1 (full) produces an output equal to the input's absolute value. Applying an input signal to R{sub}6 (positive) or R{sub}7 (negative) produces outputs of positive or negative half-cycles, respectively. Figure 2 illustrates all three modes of operation.