Question

The diagram shows a bridge rectifier circuit. A sinusoidal input voltage is fed into four identical diodes. each represented by the standard diode circuit symbol. The symbol indicates the direction of conventional current flow through the diode. The plots show input and output voltages versus time. Note that the output voltage is strictly in one direction. Explain

(a) how this circuit produces the unidirectional output voltage it does, and

(b) what features in the output plot indicate that the band gap of the diodes is about half an electronvolt, (It might seem that about one volt is correct, but consider how many diodes are on and in series at any given instant. In fact, although not the usual habit, it might be more accurate to plot the output voltage shifted upward relative to the input.)

Short answer

(a) The circuit produces unidirectional voltage because current is allowed to flow only in forward biased condition.

(b) The feature that band gap of diode is about half electron volts is output voltage.

Step-by-step solution

Given data

Determine the way a circuit produces unidirectional voltage and the output plot.

Definition of a Bridge Rectifier

A bridge rectifier is a device that is used to convert the alternating current ( AC) to direct current (DC).

In short it rectifies the mains ACinput to DCoutput. It has a wide range of applications is electric devices.

Explain how circuit produces unidirectional voltage.

(a)

A bridge rectifier is a device that is used to convert the alternating current (AC) to direct current ( DC).

In short it rectifies the mains AC input to DC output. It has a wide range of applications is electric devices.

The current in the diode is allowed to flow only when it is connected with the forward biased condition.

So, there will be an output voltage only when the direction of the input voltages agrees with the current flow direction of the diode, else no current will be allowed by the diode and thus, there will be no output voltage for that direction. So, the output voltage is unidirectional.

Therefore, the circuit produces unidirectional voltage because current is allowed to flow only in forward biased condition.

When the input's top is high-V, current travels via the upper-right diode, out the output's top, and back through the lower-left diode and the input's low-V. Half a cycle later, the current travels from the bottom high-V side of the input to the top of the output through the lower-right diode and then back to the top low-V side of the input through the upper-left diode.

Explain the feature in output plot that indicates band gap of diode is about half electron volts.

(b)

A bridge rectifier is a device that is used to convert the alternating current (AC ) to direct current ( DC).

In short it rectifies the mains AC input to DC output. It has a wide range of applications is electric devices.

The circuit is a series circuit of two groups of the diodes, here each group of the diodes are connected in parallel.

So, when each diode decrease the voltage by $V_0$, each group of parallel diodes will also decrease the voltage by $V_0$.

In case of two groups in series the decrease in the voltage is:

$$\begin{gathered} 2V_0=1V \\ {V}_0=0.5V \end{gathered}$$

Thus, the output voltage is $0.5\mathrm{V}$.

Therefore, the energy gap is $0.5\mathrm{eV}$.

Therefore, the feature that band gap of diode is about half electron volts is output voltage.