Question

anyoen who has done HW12 Q no 2 please help...

Answer 1

my question is

As part of your job as an engineer, your company has asked you to design a new regulator. Before actually doing the design, let's do some calculations. For your results you may consider the BJT, diode and the amplifier to be ideal (A→∞, Zin→∞, Zout=0).

(a) Write an expression for the output voltage (Vout) when the input voltage is below the Zener voltage (Vin<VZ). The answer should only be a function of resistances and input voltage.


(b) Consider the case when input voltage is above the Zener voltage Vin>VZ and, for now, assume RZ=0. Write an expression for the output voltage as a function of VZ and resistances.


Now we are ready for the actual design. The goal of your project is to select the appropriate resistances so that the output voltage is 5V±0.1V when the input voltage varies between 10V and 20V. Assume that the Zener diode you are using has a VZ=2.5V and RZ=1Ω (Notice RZ is not zero anymore!).

(c) What combination of R0, R1 and R2 satisfies the output voltage requirement?

(d) What is the minimum efficiency of your regulator if we consider a BJT with K=0.95 and a resistance of RL=100Ω is connected at the output terminal? (Hint: Notice that there are two power inputs to the circuit: the input terminal and the amplifier.)