Just a mental image... could you feed the positive offset voltage, that was the offset added to the input, to the inverting input of an opamp, and the output of the delay to the non-inverting input. The opamps output shifts the delayed signal in the negative direction, the same amount that it was originally positive shifted.

Ken

Oops! Ron, I see that's what they did in the schematic you attached in post #81.

 

Just a mental image... could you feed the positive offset voltage, that was the offset added to the input, to the inverting input of an opamp, and the output of the delay to the non-inverting input. The opamps output shifts the delayed signal in the negative direction, the same amount that it was originally positive shifted.

Ken

I plan on accomplishing this project in the next 2 weeks.

Can you please explain what AC coupling really is? and DC offset? I still don't understand it fully.

Thanks.

 

Ron H,

Can you please summarize what circuit i should put on the input and which one on the output?

Thanks.

 

Ron H,

Can you please summarize what circuit i should put on the input and which one on the output?

Thanks.

What is the range of your A/D converter (low and high voltage limits)?

 

What is the range of your A/D converter (low and high voltage limits)?

No specs on the ADC yet. First need to get the delay line working. It might be an Sigma-Delta one. ADC is second part of the project.

Like i said, i need to get the delay working first.

Thanks.

 

No specs on the ADC yet. First need to get the delay line working. It might be an Sigma-Delta one. ADC is second part of the project.

Like i said, i need to get the delay working first.

Thanks.

OK, but the circuit you put on the output depends on the A/D specs.

 

OK, but the circuit you put on the output depends on the A/D specs.

What about the input?

and for the output, just tell a rough circuit, schematic, from which i can read the output. Should it be the source follower or the sample & Hold?

 

What about the input?

and for the output, just tell a rough circuit, schematic, from which i can read the output. Should it be the source follower or the sample & Hold?

I already told you that you need to operationally bias the input up to a DC level that yield the least distortion of the signal waveform. I'm guessing that will be around +3 to +4V, if you are powering the BBD from +5V. I don't know if AC coupling will suffice, or if you will need a DC level shifter.
You should also amplify the input signal in order to get the best signal-to-clock-noise performance in the BBD. I would start at 1V p-p, and vary that until the output looks the best (lowest distortion and signal-to-clock-noise).

On the output, I like the source follower and S&H internal to the BBD, as I drew in my schematic. Externally, you need a low pass filter to remove the remaining clock, followed by an operational level shifter and amplifier to fit the signal into the input range of your A/D. To minimize the quantization noise, you need the p-p signal to be nearly as high as the p-p input range of the A/D.

 

I already told you that you need to operationally bias the input up to a DC level that yield the least distortion of the signal waveform. I'm guessing that will be around +3 to +4V, if you are powering the BBD from +5V. I don't know if AC coupling will suffice, or if you will need a DC level shifter.
You should also amplify the input signal in order to get the best signal-to-clock-noise performance in the BBD. I would start at 1V p-p, and vary that until the output looks the best (lowest distortion and signal-to-clock-noise).

On the output, I like the source follower and S&H internal to the BBD, as I drew in my schematic. Externally, you need a low pass filter to remove the remaining clock, followed by an operational level shifter and amplifier to fit the signal into the input range of your A/D. To minimize the quantization noise, you need the p-p signal to be nearly as high as the p-p input range of the A/D.

I apply the DC offset using the circuit you used??


When the action potential is detected, the voltage is in microvolts. It is ten amplified using a 5 transistor amplifier to millivolts and volts. So i guess i will be using amplifiers anyway. That's a big issue.


Thanks.

 

I apply the DC offset using the circuit you used??

Which circuit?

 

Which circuit?

The one you showed in your LT Spice simulation.

 

The one you showed in your LT Spice simulation.

It has an adjustable series power supply for offset. I don't think you can build a circuit like that.

 

It has an adjustable series power supply for offset. I don't think you can build a circuit like that.

Okay, then how do i do the DC offset at the input?

 

Okay, tell me, what i need to add to my bucket brigade?

Like at the input, DC offset.....what type of circuit would that be?

 

Okay, then how do i do the DC offset at the input?

What would you have done if you hadn't stumbled onto your sugardaddy (me)?

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

Part of the learning process is learning how to design. If I hand you a circuit, you learn almost nothing. You will find that, when you get into a real job, there won't always be guys like me to hand you circuit designs. Op amp circuits are very straightforward. you just have to put in a little effort to learn to design them, instead of getting the entire project designed for you, piecemeal.

 

What would you have done if you hadn't stumbled onto your sugardaddy (me)?
Part of the learning process is learning how to design. If I hand you a circuit, you learn almost nothing. You will find that, when you get into a real job, there won't always be guys like me to hand you circuit designs. Op amp circuits are very straightforward. you just have to put in a little effort to learn to design them, instead of getting the entire project designed for you, piecemeal.

Haha, i appreciate the encouragement,

but i am a little less on time. Plus, even if you give me the circuit, there is no guarantee that it will work. Your LT Spice simulation works, my Cadence one doesn't. That's why i come here for help. Even if you give the entire circuit, i still have to check it on my own and create a report for the project. So i need to learn it anyway. That's how i was going through those datasheets and scouring for clues.

I need help in going in the right direction.

I have to complete this in the next two weeks.

 

So Ron H,

I plan on simulating this further today, please help me in that regard.

Thanks.

 

I plan on accomplishing this project in the next 2 weeks.

Can you please explain what AC coupling really is? and DC offset? I still don't understand it fully.

Thanks.

I don't mean to interrupt, but have you had ANY electronics classes prior to this project? Wasn't there a class on anything other than using Cadence?

I'm just curious. You seem to be missing a vast amount of basic concepts. That is the fault of the school for not ensuring you understand the prerequisites.

 

I don't mean to interrupt, but have you had ANY electronics classes prior to this project? Wasn't there a class on anything other than using Cadence?

I'm just curious. You seem to be missing a vast amount of basic concepts. That is the fault of the school for not ensuring you understand the prerequisites.

Hi,

I have taken classes in Electrical and Electronics. And actually, i didn't have a single class in Cadence, as that is part of the task, to learn it. But Cadence is fine, it's just the results don't make sense at the moment, so i have to modify the circuit.

I don't understand what asking for AC coupling has to do with not taking classes?

My concern is, that as this BBD has been done before like in the SAD1024 and MN 30XX chips, i've been trying to use the same concept, so why is it not working? That's where Ron H's suggestion of ac coupling and DC offset come in, and if it is a solution that he suggests, then i guess it's not wrong asking for a little more clarification.


Like i said, i have to present a report, so regardless of the exact design, i need to know it very well anyway.

 

I don't mean to interrupt, but have you had ANY electronics classes prior to this project? Wasn't there a class on anything other than using Cadence?

I'm just curious. You seem to be missing a vast amount of basic concepts. That is the fault of the school for not ensuring you understand the prerequisites.

Thanks. I didn't realize anyone else was reading this thread.