Thanks for the informative post. So what you mean is, that the entire waveform must be shifted vertically so that all of it appears only on the +ve side? and then that should be fed into the BBD?

Yes. I don't think there is any way to get true DC response from a BBD. See the attached schematic, copied from the MN3207 datasheet. Notice that the input to the chip is AC coupled to an adjustable DC level.
You can learn a lot from datasheets.

How about i try to split the input signal into positive and negative part and then feed them separately? But how would that be implemented, like using the inverter?

That won't work.

Basically, right now i was thinking maybe my circuit is not giving the output as desired, as the input signal fluctuates b/w +ve and -ve.

If you see, you can clearly see some delay, however there are too many 'bars' or spikes in the output.

The bars and spikes can be removed with a sample and hold. Have you tried one yet? You would still need a filter, but it would not have to remove so much clock crap.

 

Yes. I don't think there is any way to get true DC response from a BBD. See the attached schematic, copied from the MN3207 datasheet. Notice that the input to the chip is AC coupled to an adjustable DC level.
You can learn a lot from datasheets.
That won't work.

The bars and spikes can be removed with a sample and hold. Have you tried one yet? You would still need a filter, but it would not have to remove so much clock crap.

Okay i will try and let you know.

Please explain a bit more how the signal input coupling with dc source would work.

Like what circuit should i implement? Currently i am simply using a pulse generator with the rough settings to give output for the action potential signal. You can see the rough edges in the earlier attached snapshots.

 

This is getting tedious. Don't take this the wrong way, but you are woefully unprepared to take on this task.
Why are you planning to design and fabricate a BBD to delay an action potential?

 

This is getting tedious. Don't take this the wrong way, but you are woefully unprepared to take on this task.
Why are you planning to design and fabricate a BBD to delay an action potential?

It might be tedious, but then i am learning and willing to learn.

It's part of my project. I am still an Undergraduate.

I don't think it matters what exact signal we need to delay. I mean, let's assume we have to delay a sine wave, with both positive and negative components.

You have guided me in the right direction so far, and i very much appreciate your time and effort. But please help me with hints so i can complete this task.

 

Okay i will try and let you know.

Please explain a bit more how the signal input coupling with dc source would work.

Like what circuit should i implement? Currently i am simply using a pulse generator with the rough settings to give output for the action potential signal. You can see the rough edges in the earlier attached snapshots.

Use a circuit similar to the one I posted in post #81. I would probably shoot for a signal amplitude of ≈1V p-p, with an adjustable DC offset. Measure harmonic distortion to select the optimum offset voltage. You don't need the input filter unless you anticipate input signal energy at a frequency that would be nearing the Nyquist frequency.

I would use a potentiometer instead of selectable resistors to adjust the offset.

 

Here is some background material. You may have seen it already.

 

Here is some background material. You may have seen it already.

Okay, i will try to implement the DC offset over the next couple of days. Also, when the signal comes out, hopefully after the delay, how should i pull it down to it's original form, like the +ve and -ve of the signal waveform?

 

Okay, i will try to implement the DC offset over the next couple of days. Also, when the signal comes out, hopefully after the delay, how should i pull it down to it's original form, like the +ve and -ve of the signal waveform?

AC coupling should work pretty well.

 

AC coupling should work pretty well.

AC coupling at the output end????

 

AC coupling at the output end????

Yes. Connect a capacitor from the BBD to a resistor, which connects to ground (or whatever voltage you choose) on the other end. Take the signal from the junction of the capacitor and the resistor.

 

Sounds like penumbra wants the delayed signal to have a reestablished DC level to match the input. Did they ever say what they wanted to do with the delayed signal?

Ken

 

Sounds like penumbra wants the delayed signal to have a reestablished DC level to match the input. Did they ever say what they wanted to do with the delayed signal?

Ken

Hi,

What i meant was the the signal should be pulled down again, so i get back the +ve and -ve parts.


We want to implement the delay signal into an ADC. Therefore, the bucket brigade acts as a buffer for the ADC.

 

Here is my humble opinion:

If your goal is to create a BBD device, you should have researched it enough to realize that it is not a precision analog delay line, with good DC response.
If your goal is to analyze action potentials,you should have chosen a digital approach.

 

Here is my humble opinion:

If your goal is to create a BBD device, you should have researched it enough to realize that it is not a precision analog delay line, with good DC response.
If your goal is to analyze action potentials,you should have chosen a digital approach.

I know digital is easier, however the chip we are fabricating is based on entirely analogue components. No digital stuff, not even basic Gates.

The idea is to have system, ready to function without the added complexity of programming. In any case digital system would consume too much power for our application.

Also, i think it should be fine once i figure out how to feed the -ve component of the waveform into the signal input. I'll try the dc coupling like you said and see the results.

If it can work with the audio signals, then why can't it work here?

 

I know digital is easier, however the chip we are fabricating is based on entirely analogue components. No digital stuff, not even basic Gates.

The idea is to have system, ready to function without the added complexity of programming. In any case digital system would consume too much power for our application.

Also, i think it should be fine once i figure out how to feed the -ve component of the waveform into the signal input. I'll try the dc coupling like you said and see the results.

If it can work with the audio signals, then why can't it work here?

Audio does not extend to DC. You are wanting to preserve the DC level of the signal. Audio can be AC-coupled at input and output.

 

Audio does not extend to DC. You are wanting to preserve the DC level of the signal. Audio can be AC-coupled at input and output.

I didn't quite understand what you mean by Audio not extending to DC.

It's a simple waveform, should be fine to transfer it as a series of charges....No?

 

I didn't quite understand what you mean by Audio not extending to DC.

It's a simple waveform, should be fine to transfer it as a series of charges....No?

The bandwidth of audio has a low frequency cutoff of about 20Hz, meaning it can be AC coupled with no loss of information.
Audio can be biased (by AC coupling or DC offset) to a DC level that will pass through the BBD with minimal distortion. At the output, it can be AC coupled back to ground, so it can be fed to a loudspeaker without any DC current flowing through the voice coil.
I don't think you can level shift your action potential to an optimum DC level, pass it through the BBD, and then level shift it back down to its original DC level. I think BBDs have gain and offset errors that would preclude this, but I have no proof of it. You could try it.

 

The bandwidth of audio has a low frequency cutoff of about 20Hz, meaning it can be AC coupled with no loss of information.
Audio can be biased (by AC coupling or DC offset) to a DC level that will pass through the BBD with minimal distortion. At the output, it can be AC coupled back to ground, so it can be fed to a loudspeaker without any DC current flowing through the voice coil.
I don't think you can level shift your action potential to an optimum DC level, pass it through the BBD, and then level shift it back down to its original DC level. I think BBDs have gain and offset errors that would preclude this, but I have no proof of it. You could try it.

Hi,

Why is my action potential different than the audio signal? Besides, BBD was used to delay the lines in Television, like in Europe. So the application was not just limited to audio. BBD should be able to store charge and forward it.

Are you saying my signal cannot be AC coupled? Isn't that what you did with your LT Spice model?

Thanks.

 

Hi,

Why is my action potential different than the audio signal? Besides, BBD was used to delay the lines in Television, like in Europe. So the application was not just limited to audio. BBD should be able to store charge and forward it.

Are you saying my signal cannot be AC coupled? Isn't that what you did with your LT Spice model?

Thanks.

Yes, it can be AC coupled. Once you have done this, how do you reestablish the baseline level on the output?

 

Yes, it can be AC coupled. Once you have done this, how do you reestablish the baseline level on the output?

Hi,

What do you mean by baseline level on the output?

Can you please explain why we are coupling with AC in the first place?