Question

Solution 2: An alternative to using a voltage divider is to find a way to convert one DC voltage source into another DC voltage source. If you Google "how to convert DC voltage" you will see a number of ways to do this. One such way is to use an off-the-shelf, very cheap device (<$2) called the LM317 as well as a pair of resistors. See Fig. 2. Do not concern yourself with how the LM317 works, but rather on what it does. These are the only things you need to know: 1. The LM317 is a 3 terminal device. All your other components so far have had only two terminals. 2. Terminal 3 is the 'input' terminal. This is where you connect the positive terminal of your existing voltage supply V_s (e.g. either your 5 V or 12 V fixed voltage source on your power uspply) 3. Terminal 2 is the 'output' terminal. Terminal 2 will be the positive terminal for your new voltage source 4. Terminal 1 is the 'adjust' terminal. It forces 50 ??A of current in to the node which connects Terminal 1 with R_1 and R_2. This 50 ??A is denoted I_adj in the figure. 5. The voltage across R_1 is always 1.25 V. This voltage can be denoted as V_ref. Task 3B: Determine a generic (i.e. algebraic) equation (in terms of R_1, R_2, I_adj, and V_ref) for the total output voltage based on the above 5 points. Fig. 2. A DC voltage converter which uses the LM317 device, an input voltage source V_s, and a voltage divider network. Task 3B Result Upload your working here which shows the output voltage as a function of R_1, R_2, I_adj and V_ref. Hint 1: Use Kirchhoff's Current Node Law to determine the current flowing through R_2 Hint 2: Use Kirchhoff's Voltage Loop Law to dermine the total voltage across both R_1 and R_2.

Solution 2:

An alternative to using a voltage divider is to find a way to convert one DC voltage source into another DC voltage source. If you Google "how to convert DC voltage" you will see a number of ways to do this. One such way is to use an off-the-shelf, very cheap device (<$2) called the LM317 as well as a pair of resistors. See Fig. 2.
Do not concern yourself with how the LM317 works, but rather on what it does.
These are the only things you need to know:
1. The LM317 is a 3 terminal device. All your other components so far have had only two terminals.
2. Terminal 3 is the 'input' terminal. This is where you connect the positive terminal of your existing voltage supply V_s (e.g. either your 5 V or 12 V fixed voltage source on your power uspply)
3. Terminal 2 is the 'output' terminal. Terminal 2 will be the positive terminal for your new voltage source
4. Terminal 1 is the 'adjust' terminal. It forces 50 ??A of current in to the node which connects Terminal 1 with R_1 and R_2. This 50 ??A is denoted I_adj in the figure.
5. The voltage across R_1 is always 1.25 V. This voltage can be denoted as V_ref.

Task 3B: Determine a generic (i.e. algebraic) equation (in terms of R_1, R_2, I_adj, and V_ref) for the total output voltage based on the above 5 points.

Fig. 2. A DC voltage converter which uses the LM317 device, an input voltage source V_s, and a voltage divider network.

Task 3B Result
Upload your working here which shows the output voltage as a function of R_1, R_2, I_adj and V_ref.
Hint 1: Use Kirchhoff's Current Node Law to determine the current flowing through R_2
Hint 2: Use Kirchhoff's Voltage Loop Law to dermine the total voltage across both R_1 and R_2.

Solution 2:

An alternative to using a voltage divider is to find a way to convert one DC voltage source into another DC voltage source. If you Google "how to convert DC voltage" you will see a number of ways to do this. One such way is to use an off-the-shelf, very cheap device (<2) called the LM317 as well as a pair of resistors. See Fig. 2.
Do not concern yourself with how the LM317 works, but rather on what it does.
These are the only things you need to know:
1. The LM317 is a 3 terminal device. All your other components so far have had only two terminals.
2. Terminal 3 is the 'input' terminal. This is where you connect the positive terminal of your existing voltage supply Vs (e.g. either your 5 V or 12 V fixed voltage source on your power uspply)
3. Terminal 2 is the 'output' terminal. Terminal 2 will be the positive terminal for your new voltage source
4. Terminal 1 is the 'adjust' terminal. It forces 50 ??A of current in to the node which connects Terminal 1 with R1 and R2. This 50 ??A is denoted Iadj in the figure.
5. The voltage across R1 is always 1.25 V. This voltage can be denoted as Vref.

Task 3B: Determine a generic (i.e. algebraic) equation (in terms of R1, R2, Iadj, and Vref) for the total output voltage based on the above 5 points.

Fig. 2. A DC voltage converter which uses the LM317 device, an input voltage source Vs, and a voltage divider network.

Task 3B Result
Upload your working here which shows the output voltage as a function of R1, R2, Iadj and Vref.
Hint 1: Use Kirchhoff's Current Node Law to determine the current flowing through R2
Hint 2: Use Kirchhoff's Voltage Loop Law to dermine the total voltage across both R1 and R2.

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