Feedback

APPLICATION NOTE FEEDBACK ON THE CIRCUIT NAME :

MOHD.AZLAN BIN MALLA (HK2006-6482)

21ST MARCH 2009 1.0 SUMMARY

The part of application note is to provide explanation of how the circuit is function. In this application note explain about the function of feedback on the circuit. It briefly discusses about how to measure the output voltage and the measure the value of resistor. 2.0 INTRODUCTION

Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence the same event/phenomenon in the present or future. When an event is part of a chain of cause-and-effect that forms a circuit or loop, then the event is said to "feed back" into itself. Figure below show about type of feedback.

Figure1 3.0 ISSUES

From the circuit, we know feedback is to produce or different voltage to control output voltage. So, we use the feedback to proposed ranges voltage to 500V, 800V, and 1kV.

Figure 2

Figure 3

4.0 PROBLEM (WHY IT FAILS)

Why we have to calculate the value of R2? To make sure that the voltage flow across zener diode is 20V. The voltage must less than 20V to turn ON the zener diode. Through voltage divider calculation, if we want to produce 1000V, the voltage at R2 is equal to the value of zener diode thet is 20V. So, voltage at R1 equal to 980V. Apply calculation, (Figure 4)

Figure 4

But, as we apply R2 = 204kΩ, the output voltage is only 900V Let’s calculate for output voltage equal to 800V. As previous, voltage at R2 is equal to 20V same as the value of zener diode. So, that’s make voltage at R1 is equal to 780V. Apply voltage divider rule, Apply calculation, (Figure 5)

Figure 5

But as we apply R2 equal to 256kΩ, the output voltage we get also 900V . What we found that the output voltage in theory is much different from what we achieved in the circuit. There goes the same to output voltage equals to 500V. Through voltage divider rules calculation is equal to 20V through we apply R2 equals 416kΩ, but still we get output voltage equal to 900V.

5.0 CONCLUSION Through our observation on the three experiment of feedback that we applied for different value of resistor, to produce different voltage, all the experiment results produce the same output voltage that is 900V. So we conclude that, the feedback is not suitable to be applied in our circuit.