PARALLEL-NEGATIVE LIMITER WITH BIAS. - The circuit shown in figure 4-13, view (A), is a parallel-negative limiter with negative bias. With no input, the battery maintains D1 in a reverse-bias condition. D1 cannot conduct until its cathode is more negative than its anode. D1 acts as an open until the input signal dips below -4 volts at T2 in view (B). At T2 the input signal becomes negative enough to forward bias the diode, D1 conducts and acts like a short, and the output is limited to the -4 volts from the battery from T2 to T3. Between T3 and T4 the diode is again reverse biased. The output signal follows the input signal and no limiting occurs.

Figure 4-13A. - Parallel-negative limiter with negative bias.

Figure 4-13B. - Parallel-negative limiter with negative bias.

Figure 4-14, view (A), shows a parallel-negative limiter with positive bias. The operation is similar to those circuits already explained. Limiting occurs when the diode conducts. No limiting occurs when the diode is reverse biased. In this circuit, the bias battery provides forward bias to the diode without an input signal. The output is at +4 volts, except where the input goes above +4 volts (T1 to T2), as shown in view (B). The parts of the signal more negative than +4 volts are limited.

Figure 4-14A. - Parallel-negative limiter with positive bias.

Figure 4-14B. - Parallel-negative limiter with positive bias.

Q.4 What component is in parallel with the output in a parallel limiter?
Q.5 What is the condition of the diode in a series limiter when an output is developed? In a parallel limiter?