- Question 4 8 Marks A Friend Has Designed A Series Voltage Regulator Circuit That Is Not Working To Specification The 1 (104.01 KiB) Viewed 55 times
Question 4 [8 marks] A friend has designed a series voltage regulator circuit that is not working to specification. The circuit diagram is shown in Figure 5. The component values chosen in the design are summarised in Table 1. You have offered your assistance to review the design and identify errors. The specifications of the regulator are listed below: • Input voltage: V = 24 V Regulated output voltage: Vreg = 18 V Maximum output current lout(max) = 1.11 A Short circuit current loutisc) = 0.21 A Assume that VBE, Q1 = 1.4 V and VBE, Q2 = 0.7 V when Q: and Q are switched ON respectively. Furthermore, assume that the value of resistor R, has been chosen correctly and the op-amp, and transistors Q: and Q₂ cannot be changed. Table 1: values of components used in the series voltage regulator circuit Component label Value R₁ 8 ΚΩ R₂ 3 ΚΩ R₂ 1 ΚΩ R₁ 492 R$ 252 R₂ 102 R₂ Assume value chosen correctly R₁ Vary from 10 k2 to 02 D₁ 6V @ -2mA Q₁ Power transistor, VBE, Q1 = 1.4 V Low power transistor VBE, Q2 = 0.7 V Q₂ 2₁ R₂ V₂ Vo W WI R₂ R6 www 2₂ R₂ www D₁ 8002 VE Figure 5: voltage regulator circuit 4.1 Identify and explain the two errors in the design of the series voltage regulator. Examples of errors are mistakes in the connections of components in the circuit diagram, incorrect component values or incorrect components used. [4] [4] 4.2 Propose solutions to fix the two errors identified in question 4.1. V₁ ww lout VreB R₂ R₂ W +₁ R₁₂