Question

For a half-wave rectifier (assume ideal diodes) with NO smoothing/filtering capacitor and whose voltage source peak is Vs=80V and load RL=1k Consider the two following diodes:

(a) Diode1: breakdown voltage =-100V, and current rating = 100mA
(b) Diode2: breakdown voltage =-90V, and current rating = 100mA
(c) Diode3: breakdown voltage =-170V, and current rating = 90mA
(d) Diode4: breakdown voltage =-180V, and current rating = 90mA

When the circuit diodes break, the following diodes can be used for replacement:

a. None
b. Diode 4
c. All diodes
d. Diodes 3 and 4

Answer 1

For a half-wave rectifier circuit with no smoothing capacitor, Diodes 3 and 4 can be used as replacements because they have the necessary breakdown voltage and current rating.

Step-by-step explanation:

For the given circuit, a half-wave rectifier with ideal diodes and no smoothing capacitor, we are asked to determine which diodes can be used for replacement.

In a half-wave rectifier, the diode conducts only during the positive half-cycle of the AC input voltage. This means that the diode conducts when the voltage is greater than 0.7 V (approximately) and there is no current flow during the negative half-cycle.

Therefore, for a diode to work as a replacement, it should have a breakdown voltage greater than 80V and current rating greater than 1mA. From the given diodes, only Diode 3 and Diode 4 satisfy these conditions.

Answer 2

For the half-wave rectifier circuit in question, both Diode3 and Diode4 are suitable replacements due to their breakdown voltage and current rating, which meet the circuit's requirements.

Step-by-step explanation:

When selecting circuit diodes for a half-wave rectifier with a peak voltage of Vs=80V and a load resistance (RL) of 1k ohms, one must consider both the breakdown voltage and the current rating of the diodes. The breakdown voltage should be greater than the peak reverse voltage that the diode will encounter, and the current rating should be greater than the expected maximum current through the circuit diode.

The peak reverse voltage for the half-wave rectifier will be 80V. Thus, a suitable diode for replacement needs to have a breakdown voltage greater than 80V. Given the diodes, Diode3 with a breakdown voltage of -170V and Diode4 with a breakdown voltage of -180V, exceed this requirement.

However, we must also ensure that neither the peak nor the average current exceeds the diode's current rating. With a 1k ohm load, the peak current will be Vs/RL = 80V/1000ohms = 80mA, which is below the 90mA rating of both Diode3 and Diode4. Therefore, both Diode3 and Diode4 can be used as replacements in the mentioned rectifier circuit.