Hi there, I currently try to design an AD converter as simple as possible (for didactical reasons). It should be able to act as a 3bit converter on a time-dependent signal. It should preferably output a quantised signal (blue) from an analogue input (red)


If possible I only want to use opamps, resistors and (maybe And/Nand gatter). I started with a basic flash converter and feel that if I could sum the outputs of all comparators properly I would get the desired blue curve. Nevertheless my idea to just add an opamp summing amplifier didn't work at all.



Any idea how I could go on from here? I would appreciate any help.

 

Try using comparator(s) to convert the analog signal to digital output.
You'll need to use window comparators as well.

I would use arbitrary behavioral devices to do the conversion.

 

 

TTry to plot this:
(V(a0)+V(a1)*2+V(a2)*4)/25

 

TTry to plot this:
(V(a0)+V(a1)*2+V(a2)*4)/25
View attachment 223507View attachment 223507

I took Ron's schematic and converted it using all a devices.
See attached.

Files attached below.

 

See

 

I took Ron's schematic and converted it using all a devices.
See attached.

Files attached below.

View attachment 223613

Thanks eetech00,

that's actually beautiful.
I recognise the three OR-gates to the right as a normal 8-(7)-3 binary encode. But what's the job of the XORS? Is it only to prove that at one time only one input at high might enter the OR-gates? I do not really catch it.

 

Thanks eetech00,

that's actually beautiful.
I recognise the three OR-gates to the right as a normal 8-(7)-3 binary encode. But what's the job of the XORS? Is it only to prove that at one time only one input at high might enter the OR-gates? I do not really catch it.

Yes. During an input signal transition, the first input high of an XOR gate will get precendence.