Wave Shaping

Dual-Diode Limiter

The next type of diode limiter to be discussed is the dual-diode limiter, shown in the figure below, view A. This limiter combines a parallel-negative limiter with negative bias (D₁ and V₁) and a parallel-positive limiter with positive bias (D₂ and V₂). Parts of both the positive and negative alternations are removed in this circuit. Each battery aids the reverse bias of the diode in its circuit; the circuit has no current flow with no input signal. When the input signal is below the value of the biasing batteries, both D₁ and D₂ are reverse biased. With D₁ and D₂ reverse biased, the output follows the input. When the input signal becomes more positive than +10 volts (view B), D₂ conducts and limits the output to +10 volts. When the input signal becomes more negative than -10 volts, D₁ conducts and limits the output to this value. When neither diode conducts, the output follows the input waveform.