4-26 At T3 the input and capacitor voltages are series aiding and the total output voltage is -50 volts. From T3 to T4, D1 is reverse biased and C discharges through R. The circuit operation is now the same as it was from T1 to T2. The circuit operation for the following square-wave cycles duplicates the operation which occurred from T1 to T3. As was the case with the positive clamper, the amplitude and wave, shape of the output is almost identical to that of the input. However, note that the upper extremity of the output wave shape is clamped to 0 volts; that is, the output wave shape, for all practical purposes, lies entirely below the 0-volt reference level. Negative-Diode Clamper With Negative Bias View (A) of figure 4-22 is the circuit of a negative clamper with negative bias. Again, with no input signal the capacitor charges to the battery voltage and the output is negative because the positive side of the battery is ground. The bottom of view (B) shows the output of the circuit. Study the figure carefully, and note the following important points. The peak-to-peak amplitude and shape of the output wave, for all practical purposes, are the same as that of the input wave. The output wave is clamped to -10 volts which is the value of the battery. Since this is a negative clamper, the upper extremity of the waveform touches the -10 volt reference line (and the rest of it lies below this voltage level). Figure 4-22A.—Negative damper with negative bias.
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