How to boost voltage of signal generator frequency?

Okay, here's the question/challenge...

I'm using an AD9850 signal generator IC to create various frequencies which works great. Input voltage is 5-volts. However the output is only around .5-volts.

What I need is to be able to boost that to (ideally) around 45-volts without affecting the frequency created. The ultimate amperage I am working with is only 20-600 microamps so the boost shouldn't be a problem (I think). I've independently used voltage boosters but wonder if those affect the frequency.

Then from there I want to make the current biphasic (reversing polarity every 3-5 seconds) so I'm assuming a relay somewhere at this end.

What say the resident experts here?

sort by: active | newest | oldest
iceng2 years ago

Here are two versions of a 600uA opto H bridge frequency controlled by your AD9850.

If the signal is only 0.5 volt then use an op-amp or comparator to reach a 5 volt swing for this bridge.

pletchman (author)  iceng2 years ago

As always -- you rock Iceng. I'm going to start putting the components together and testing things. Thanks for the direct and detailed assistance. Of course I'm sure I'll be checking back here as I finish things off. Thanks again.

iceng pletchman2 years ago

You should know the quad ILQ device each output NPN transistor can withstand 70 VDC across the collector emitter, known as Vce=70v...

While many of the single opto-isolstors are only Vce=30v

pletchman (author)  iceng2 years ago

Thank you Iceng. I was putting together the 4 optocoupler configuration with PC817 which are only rated to 35v. May be fine but I think I'll just go for the quad opto IC since its fewer discrete components anyways and the Vce rating is more than adequate.

iceng pletchman2 years ago

Easy enough to make a wire mistake with the ILQ 16 PIN IC.......

THAT sir, is a very sneaky arrangement of components. I salute you.

Thks :)

RohanP111 year ago

sir,which driver could be given frq. About 1MHZ

pletchman (author) 2 years ago

That's the challenge. The frequency is going to range anywhere from 1hz to 1000z with a variable amplitude of 20-600 microamps

-max- pletchman2 years ago

A good operational amplifier set up using a non-inverting amp configuration will easily achieve that. Used in the non-inverting configuration, it will take the input and multiply it by some fixed amount depending on the resistors used. You can find the circuits and calculations online.

What load do you want to deliver this current into ?

pletchman (author)  steveastrouk2 years ago

It's replicating a medical device that delivers micro current with variable frequencies through the body. It uses conductive pads to reduce the resistance.

-max-2 years ago

A class A amplifier maybe? To get high DC voltage output presicion, I would also use a negitive ffedback loop and up amp stage.

I'd use a working keyboard....

Yeah, I don;t know how so many typos ended up in that. Oh well

Yeah, I don;t know how so many typos ended up in that. Oh well

-max- -max-2 years ago

Op amp stage*

pletchman (author) 2 years ago

So let me ask this... If the frequency is already established and I create the DC 45-volt current independently -- how do these "merge" together to create a 45-volt current carrying whichever frequency was initially established?

That's what the amplifier DOES. All you need is a modest audio amp. The voltage an ordinary voltmeter shows may or may not be correct at any frequency other than mains. It depends on the quality of the meter.

You seem terribly confused about voltage and current. You can't have a 48V current !

pletchman (author)  steveastrouk2 years ago

Sorry, I put the two together. I completely understand the difference between the voltage and the amperage.

All you need is an amplifier, the spec depends on frequency. Do you want 48 V amplitude, or peak to peak ?

What frequency ?

pletchman (author)  steveastrouk2 years ago

Also, this may sound like a naive answer, but whichever voltage is the one that a regular multimeter displays when checking DC voltage

If you lack the most basic things about voltage, current and elektronics I see hard times coming for you.

We talk apples, you understand oranges...

Are you sure it is a good idea to start messing with electronics yourself?

Might be better to ask someone with a bit more knowledge for assistance....

No offence!

rickharris2 years ago

A power amplifier n the output . The output frequency may be an issue.