Understanding the Output Voltage of a Transistor Circuit with a Zener Diode

[cpburris]

Homework Statement

https://www.circuitlab.com/circuit/8ekkzw/dfsgadsfgdafgh/

For the circuit, suppose that the input voltage V_in is a superposition of 18 V DC and a sinusoidal component with a 6 V amplitude (thus the input voltage varies between 12 V and 24 V). Diode D1 is a 4.3 V zener diode. Describe the output voltage V_out.

The Attempt at a Solution

[/B]
Spent three hours already trying to figure it out, but I am just not getting anywhere.

 

[berkeman]

Homework Statement

https://www.circuitlab.com/circuit/8ekkzw/dfsgadsfgdafgh/

For the circuit, suppose that the input voltage V_in is a superposition of 18 V DC and a sinusoidal component with a 6 V amplitude (thus the input voltage varies between 12 V and 24 V). Diode D1 is a 4.3 V zener diode. Describe the output voltage V_out.

The Attempt at a Solution

[/B]
Spent three hours already trying to figure it out, but I am just not getting anywhere.

We need more work from you before we can be of much help. Show us what all the node voltages are for 3 cases -- Vin = min, Vin = max, Vin = 18V...

 

[Hesch]

cpburris: Ask yourself two questions:

1) What will happen if V_out > 5V ?

2) What will happen if V_out < 5V ?

( Assuming that V_be = 0.7V ).