Question

help with number 1 please

1. The cireuit shown to the right is a bridge rectifier. The output voltage, Vour, is taken across the load resistor in the middle of the bridge a. I built this circuit in an attempt to make a full wave rectifier, but it does not work! What do I need to do to fix it and why? Tell me how to fix it and draw the correct circuit. (You may want to complete Part (b) first to help with this.) b. For the circuit as drawn above, assume the input voltage is a sinusoidal signal with an amplitude of 4 V. Draw a single plot with ViN and Vour versus time. Positive voltage polarity is shown on the diagram. Your voltage scale must be aceurate but you may use an arbitrary time scale e. For the circuit after you have fixed it, draw a single plot with Vis and Vour versus time. Positive voltage polarity is shown on the diagram. Your voltage scale must be accurate but you may use an arbitrary time scale. Assume the same assume the input voltage as the previous part.

Answer 1

a,b) The circuit given in the problem is shown in the image below.

vt 2-gv 1B 2 2 Tmput is shown in blue color tput is shown im Ted Coler o u

Let at any time point B is at positive voltage and point A is at negative voltage, so from the circuit it is clear that only diode 2 and 4 are in forward bias and 1, 3 are in reverse bias, so current flows through diode 4, resistor and diode 2 and we get voltage across resistor which is less than input voltage (4V) because in forward bias there is voltage drop across the diode which depends on the material of the diode, in general it is about 0.6V to 0.7V. so we get out put less than 4V.

Now consider the opposite case when point A is at positive voltage and point B is at negative voltage. We see that doses 1,2 and 4 is at reverse bias, so no current flows through the resistor and there no output voltage. So the circuit work as a half wave rectifier. So the circuit gives output for only one half of input sinusoidal voltage. The out put is given in the above image .

To fixed the circuit we just need to change the direction of the diode 1. So we have to connect diode 1 in opposite direction as shown in the image below.

2 2 4 rN nput is sheum m Wue Coler Ou

c) Now when the point B is positive and A is negative diode 4 and 2 are in forward bias so current flows through resistor and we get output voltage as before which is less than input voltage due to voltage drop across two diodes .

when point A is positive and point B is negative voltage we can see now from the fixed circuit that diode 1 and diode 3 are in forward bias, so current flows diode 1, resistor and diode 3 so we get output voltage. Now this circuit works as a full wave rectifier. The output voltage is shown in the above image.