Hi,
I have a question in my HND about R/2R ladders, I have been given the diagram below and asked the following question:
The diagram of FIGURE 1 shows a 3 input R/2R digital to analogue converter circuit. By working back from the output (or otherwise) to find the equivalent input resistance in order to determine the input voltage, show that the output voltage values for the following digital input combinations are as shown below.
The voltages "as shown below" are:
1) When A= 1, B = 0 and C = 0 the output = 1/12 of Vin
2) When A= 0, B = 0 and C = 1 the output = 4/12 of Vin
3) When A = 1, B = 1 and C = 0 the output = 3/12 of Vin
Source: https://www.dropbox.com/s/6k5utzcy41isudy/R2R.jpg?dl=0
(Sorry but I cannot seem to get the image to show up, I have shared it and made it public on dropbox but it always just comes up as a red X)
The trouble is that I cannot get these answers. Also doing research online there always seems to be another 2R resistor between point E and ground.
I was struggling trying to work it out by cancelling resistors out so I have simulated the circuit in multisim and get the following for each 3 combinations:
1) 1/5 of Vin
2) 2/5 of Vin
3) 3/8 of Vin
Can anybody tell me where I am going wrong?
thanks
[Mod Edit: uploaded image to thread]
I have a question in my HND about R/2R ladders, I have been given the diagram below and asked the following question:
The diagram of FIGURE 1 shows a 3 input R/2R digital to analogue converter circuit. By working back from the output (or otherwise) to find the equivalent input resistance in order to determine the input voltage, show that the output voltage values for the following digital input combinations are as shown below.
The voltages "as shown below" are:
1) When A= 1, B = 0 and C = 0 the output = 1/12 of Vin
2) When A= 0, B = 0 and C = 1 the output = 4/12 of Vin
3) When A = 1, B = 1 and C = 0 the output = 3/12 of Vin
Source: https://www.dropbox.com/s/6k5utzcy41isudy/R2R.jpg?dl=0
(Sorry but I cannot seem to get the image to show up, I have shared it and made it public on dropbox but it always just comes up as a red X)
The trouble is that I cannot get these answers. Also doing research online there always seems to be another 2R resistor between point E and ground.
I was struggling trying to work it out by cancelling resistors out so I have simulated the circuit in multisim and get the following for each 3 combinations:
1) 1/5 of Vin
2) 2/5 of Vin
3) 3/8 of Vin
Can anybody tell me where I am going wrong?
thanks
[Mod Edit: uploaded image to thread]
Last edited by a moderator: