How to calculate this 4 bit DAC

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In summary: It should show all the input switches and all the output switches, with labels for each switch input and output, and the value of each resistor.In summary, the conversation discussed how to calculate a 4-bit DAC using the R-2R ladder. The user was struggling to understand the concept and searched for examples online, but had difficulty finding useful information. They were advised to search for R-2R ladder DAC and to double check their circuit for any mistakes. It was also suggested to connect the inputs to either 0 or 5 volts and to ensure the amplifier has a high input resistance. The user later posted a revised circuit diagram and stated they were able to solve the problem using a voltage divider. However, they encountered a problem
  • #1
michael1978
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< Mentor Note -- thread moved to HH from the technical forums, so no Homework Help Template is shown >

please can somebody help me, how to calculate this 4 bit dac,
i know this one if input 1.1.1.1 5/2, 5/4 5/8 5/16 voltage

i don't understand nothing i search on the internet but i don't find some useful example,
my english is not so good...
please one more time can somebody explain me how to calculate, for formula thanks
ice_screenshot_20170630-161958.png
 
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  • #2
michael1978 said:
i search on the internet but i don't find some useful example,
Try again, using the search terms R-2R ladder DAC.

After you have done that reading, try again to work your schoolwork problem and post your work here so we can check it.
 
  • #3
BTW, can you check your circuit, as I think the op-amp has the inputs reversed.

Berkeman beat me to the rest of the comment.
 
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  • #4
Merlin3189 said:
BTW, can you check your circuit, as I think the op-amp has the inputs reversed.
Good catch!
 
  • #5
Merlin3189 said:
BTW, can you check your circuit, as I think the op-amp has the inputs reversed.

Berkeman beat me to the rest of the comment.
thank you a lot , it help me, thanks...
have nice night.
 
  • #6
Also, you show the output component as a Comparator. It should be a Op-Amp, not a Comparator.
 
  • #7
You really should look up another version of the R 2R ladder.
-1 if key A is closed, the positive supply is short circuited to the output of the op-amp. That won't end well.
2 R1 shouldn't be there.
3 The ampiflier you connect the R-2R ladder to should have infinite (much larger than R) imput resistance.
4 The inputs should be connected to either 0 or 5 volts, and not left unconnected.

The last point is essential to make make the superposition principle work. If you have a network of resistors and voltage sources, you can calculate the effect of a single voltage source by replacing all the other voltage sources with a wire. You can than sum those indivudual effects to get the output voltage. Replacing the voltage sources by open circuits won't work.
 
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  • #8
willem2 said:
You really should look up another version of the R 2R ladder.
-1 if key A is closed, the positive supply is short circuited to the output of the op-amp. That won't end well.
2 R1 shouldn't be there.
3 The ampiflier you connect the R-2R ladder to should have infinite (much larger than R) imput resistance.
4 The inputs should be connected to either 0 or 5 volts, and not left unconnected.

The last point is essential to make make the superposition principle work. If you have a network of resistors and voltage sources, you can calculate the effect of a single voltage source by replacing all the other voltage sources with a wire. You can than sum those indivudual effects to get the output voltage. Replacing the voltage sources by open circuits won't work.
Good Morning

i solve all the problme with voltage divider i find all the values.
but the problem is, when i push key D, the voltage of D is the same(like i find it with voltage divider), but the voltage on c,b,a they have other value?
how do i calculate ?because i draw the circuit in gsm (every circuit)
thanks...
 
  • #9
The circuit in post #1 is a weird mix of several ideas.
Please post your revised circuit diagram.
 

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Related to How to calculate this 4 bit DAC

1. How does a 4 bit DAC work?

A 4 bit DAC (digital-to-analog converter) converts a 4 bit binary input into an analog output voltage. The 4 bits represent 16 different voltage levels, with each bit representing one of the levels. The digital input is converted into an analog output by using a combination of resistors and switches.

2. What is the resolution of a 4 bit DAC?

The resolution of a 4 bit DAC is 4 bits, meaning it can represent 2^4 (or 16) different voltage levels. This is because there are 4 bits in the binary input, and each bit can have a value of either 0 or 1, resulting in 16 possible combinations.

3. How do you calculate the output voltage of a 4 bit DAC?

To calculate the output voltage of a 4 bit DAC, you first need to determine the reference voltage and the input code. The reference voltage is the maximum voltage that the DAC can output, and the input code represents the binary input. Then, use this formula: output voltage = (input code / 2^4) * reference voltage. For example, if the reference voltage is 5V and the input code is 1001, the output voltage would be (9/16)*5V = 2.81V.

4. What is the advantage of using a 4 bit DAC over a higher bit DAC?

The main advantage of using a 4 bit DAC is its simplicity and cost-effectiveness. It only requires 4 bits to represent 16 voltage levels, whereas a higher bit DAC would require more bits to represent the same number of levels. This makes a 4 bit DAC suitable for basic applications where high precision is not necessary.

5. How do you choose the appropriate resistors for a 4 bit DAC?

The resistors used in a 4 bit DAC should have equal values and should be connected in a binary weighted configuration. This means that the first resistor should have a value equal to the reference voltage, and each subsequent resistor should have half the value of the previous resistor. For example, if the reference voltage is 5V, the first resistor should be 5V and the second resistor should be 2.5V, and so on. This ensures that the voltage levels are evenly spaced and the output is accurate.

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