gain control for 100Mhz

[navidrct]

hi
i build a function gen that its output frequency is about 100 MHz
i want the amplitude of wave be variable
maybe i use gain control but its expensive
i want something cheap.
anybody know a way?

[JoeB83]

I think we need more information about your project in order to help you.

[navidrct]

I think we need more information about your project in order to help you.

100 MHz . a lot of wave type . output must be between 12 and -12 .
u think of sine wave that its swing between -5 and 5
notice that i have -12 and 12 by power supply .

[JoeB83]

Can you share a schematic?

[navidrct]

Can you share a schematic?

it does not matter
i have 100MHz wave that i want be variable.do u know a way that its cheap?

[vk6zgo]

PIN diode.
http://www.radio-electronics.com/info/rf-technology-design/attenuators/rf-variable-pin-diode-attenuator.php

[navidrct]

PIN diode.
http://www.radio-electronics.com/info/rf-technology-design/attenuators/rf-variable-pin-diode-attenuator.php

i don't think that it will be good solution for function gen that has 100 MHz bandwidth

[tggzzz]

Can you share a schematic?

it does not matter
i have 100MHz wave that i want be variable.do u know a way that its cheap?

Yes it does matter.
Yes I do know a way that meets your very vague requirements.

You would be well advised not to tell people that know about these things that the answers to their questions do not matter.

[vk6zgo]

PIN diode.
http://www.radio-electronics.com/info/rf-technology-design/attenuators/rf-variable-pin-diode-attenuator.php

i don't think that it will be good solution for function gen that has 100 MHz bandwidth

I'm not saying to use that exact design,but PIN diode circuits are widely used as attenuators.
One I've worked on was at 433MHz.
In his original post,he did say 100MHz signal,not bandwidth.

OK,I should have realised what he meant when he said "function generator".

[Fungus]

i have 100MHz wave that i want be variable.do u know a way that its cheap?

Potentiometer?

[tron9000]

Can you share a schematic?

it does not matter
i have 100MHz wave that i want be variable.do u know a way that its cheap?

+1 tggzzz,

No Schematic, no dice - http://tron9000.blogspot.co.uk/2015/05/its-all-in-your-head.html

[daqq]

do u know a way that its cheap?

Define cheap. The cheapest way is to simply scale your DAC input data and trade amplitude control for loss of resolution. Depending on your DAC input type you can scale the input (reference) voltage. Variable gain amplifiers are another option. Attenuators (relay based, solid state) can get pricey, but you can scale without resolution loss over several decades when done properly.

[navidrct]

my DAC output full range is 30mA
in attachment u can see

[oldway]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

[tggzzz]

Your spec keeps on changing.

First it is 100MHz, then 100MHz bandwidth, and I suspect even that isn't correct (it certainly isn't accurate).
First it is single-ended voltage, then you introduce differential current.

You should do research on "differential transimpedance" and "reconstruction filter".

[tggzzz]

Can you share a schematic?

it does not matter
i have 100MHz wave that i want be variable.do u know a way that its cheap?

+1 tggzzz,

No Schematic, no dice - http://tron9000.blogspot.co.uk/2015/05/its-all-in-your-head.html

My variant is https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/

I encourage the OP to understand what's in it.

[navidrct]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

u mean digital resistor?
if yes
that wont work cause that cant support 100 MHz

[KJDS]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

if u mean digital resistor
that wont work
cause 100 MHz cant be supported by DR
and its not working

What makes you think that a suggestion of an adjustable amplifier can mean a digital resistor?

[navidrct]

Your spec keeps on changing.

First it is 100MHz, then 100MHz bandwidth, and I suspect even that isn't correct (it certainly isn't accurate).
First it is single-ended voltage, then you introduce differential current.

You should do research on "differential transimpedance" and "reconstruction filter".

sorry sorry that was my mistake
max freq is 100MHz

[navidrct]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

if u mean digital resistor
that wont work
cause 100 MHz cant be supported by DR
and its not working

What makes you think that a suggestion of an adjustable amplifier can mean a digital resistor?

then you mean voltage gain control that i said before its so expensive

[daqq]

then you mean voltage gain control that i said before its so expensive

OK, could you please define expensive? 1 USD? 3 USD? 5 USD? 10 USD? 20 USD?

[Fungus]

then you mean voltage gain control that i said before its so expensive

You want a 100MHz amplifier that isn't expensive? 

You're doing it wrong. But we have no idea what you're actually doing so we can't help.

I declare this thread finished until you provide a schematic.

[navidrct]

then you mean voltage gain control that i said before its so expensive

You want a 100MHz amplifier that isn't expensive? 

You're doing it wrong. But we have no idea what you're actually doing so we can't help.

I declare this thread finished until you provide a schematic.

i want variable voltage control amplifier not just an amplifier 

[oldway]

Please post in the beginner section, you seems to be a beginner.

[oldway]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

u mean digital resistor?
if yes
that wont work cause that cant support 100 MHz

Did you ever look at a schematic of a function generator ?

[navidrct]

then you mean voltage gain control that i said before its so expensive

OK, could you please define expensive? 1 USD? 3 USD? 5 USD? 10 USD? 20 USD?

in my country a VGC is about 15 US . in large scale it is expensive 

[navidrct]

It seems to me that what you need is an adjustable 50R output amplifier for your function generator.

u mean digital resistor?
if yes
that wont work cause that cant support 100 MHz

Did you ever look at a schematic of a function generator ?

yes . i have Agilent schematic of a function generator that its so old and complicated
do u have any useful?

[navidrct]

Please post in the beginner section, you seems to be a beginner.

Gooooood for U that ur not beginner 

[oldway]

You make everybody crazy here because you ever can't especificate what you want !

[Fungus]

we have no idea what you're actually doing so we can't help.

I declare this thread finished until you provide a schematic.

i want variable voltage control amplifier not just an amplifier 

Variable voltage control of WHAT? 

PS:  yourself

[oldway]

yes . i have Agilent schematic of a function generator that its so old and complicated
do u have any useful?

To amplifier a 100Mhz square wave, you need at least 10 times greater bandwith, that's a 1 Ghz bandwith amplifier...Doe you think it is not a complicated amplifier ?

[oldway]

then you mean voltage gain control that i said before its so expensive

OK, could you please define expensive? 1 USD? 3 USD? 5 USD? 10 USD? 20 USD?

in my country a VGC is about 15 US . in large scale it is expensive 

You intend to produce something in large scale ?...You are kidding...

[tggzzz]

in my country a VGC is about 15 US . in large scale it is expensive 

Why don't you specify your country?

My guess is that you think function generators are unnecessarily expensive, and that you can make cheaper ones. For that to be true one of two preconditions must be valid:

• you have a secret technical innovation that nobody else has thought of. Given your question, I doubt that very much
• you can design, procure, make, test, sell, distribute, and all the other business activities cheaper than other people. Why do you think that other people aren't already doing that?

You should research the "Dunning Krueger effect".

[Fungus]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

[navidrct]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

[navidrct]

i think i found a solution .
that was interesting that what Agilent do in its function gen .
harder for software but cheaper in hardware

[navidrct]

in my country a VGC is about 15 US . in large scale it is expensive 

Why don't you specify your country?

My guess is that you think function generators are unnecessarily expensive, and that you can make cheaper ones. For that to be true one of two preconditions must be valid:

• you have a secret technical innovation that nobody else has thought of. Given your question, I doubt that very much
• you can design, procure, make, test, sell, distribute, and all the other business activities cheaper than other people. Why do you think that other people aren't already doing that?

You should research the "Dunning Krueger effect".

thanks
but i did it in 100 MHz output in cheap way with right choose .
Agilent in function gen of old time has a method that is so cheap that i want to use
variable part of circuit was issue for being cheap
i will use it and i will show the result

[tron9000]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

WHAT? A bloody POT! Here's me getting all ...and all he needed was a flipping POT!

Worse than the ending to Revolver!

[AF6LJ]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

WHAT? A bloody POT! Here's me getting all ...and all he needed was a flipping POT!

Worse than the ending to Revolver!

That wouldn't work very well anyway.
Apparently the output flatness over frequency is not important to the designer of this FG.
There is no "cheap way" to have uniform output amplitude over a wide frequency range at those frequencies without an auto-leveling circuit.

[Fungus]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

No problem! 

[navidrct]

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

WHAT? A bloody POT! Here's me getting all ...and all he needed was a flipping POT!

Worse than the ending to Revolver!

U killing me

[SaabFAN]

My solution:

J-FET Attenuator controlled by a OpAmp that is fed with the voltage from a Peak Detector and one from a DAC. After that a simple AB-Class amplifier powered by +/-15V with the Peak-Detector connected to its output.

[AF6LJ]

My solution:

J-FET Attenuator controlled by a OpAmp that is fed with the voltage from a Peak Detector and one from a DAC. After that a simple AB-Class amplifier powered by +/-15V with the Peak-Detector connected to its output.

I would do simething similar but without the DAC.

[JoeB83]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

[navidrct]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

I had a simple question not a rocket science
Sorry but most of people here just mask fun of every word without any help.
If somebody think that I'm giving information less than usual can ignore topic.
Please if u don't get the topic just ignore please



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[tggzzz]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

I had a simple question not a rocket science
Sorry but most of people here just mask fun of every word without any help.
If somebody think that I'm giving information less than usual can ignore topic.
Please if u don't get the topic just ignore please

Even simple questions need to be approached and asked in appropriate ways.

And we do "get the topic", but you don't!

[AF6LJ]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

I had a simple question not a rocket science
Sorry but most of people here just mask fun of every word without any help.
If somebody think that I'm giving information less than usual can ignore topic.
Please if u don't get the topic just ignore please


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We get the topic; the problem is lack of information.
No we don't need a schematic, but more information would be helpful.

Is this function generator operating from DC-100MHZ?

designing an output leveling circuit is not such an easy task, how are you going to compensate for frequency change?
how about compensating for wave shape?
Are you going to be driving a 50 ohm load?

We really cannot be very helpful without more information.

[navidrct]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

I had a simple question not a rocket science
Sorry but most of people here just mask fun of every word without any help.
If somebody think that I'm giving information less than usual can ignore topic.
Please if u don't get the topic just ignore please


Sent from my HUAWEI G730-U00 using Tapatalk

We get the topic; the problem is lack of information.
No we don't need a schematic, but more information would be helpful.

Is this function generator operating from DC-100MHZ?

designing an output leveling circuit is not such an easy task, how are you going to compensate for frequency change?
how about compensating for wave shape?
Are you going to be driving a 50 ohm load?

We really cannot be very helpful without more information.

Thanks
I'm gonna use agilent way for that .
Hope it work


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[KJDS]

navidrct: Next time you ask for help please provide a schematic and try being a little less rude. This kind of shit won't fly in the real world.

I had a simple question not a rocket science
Sorry but most of people here just mask fun of every word without any help.
If somebody think that I'm giving information less than usual can ignore topic.
Please if u don't get the topic just ignore please


Sent from my HUAWEI G730-U00 using Tapatalk

We get the topic; the problem is lack of information.
No we don't need a schematic, but more information would be helpful.

Is this function generator operating from DC-100MHZ?

designing an output leveling circuit is not such an easy task, how are you going to compensate for frequency change?
how about compensating for wave shape?
Are you going to be driving a 50 ohm load?

We really cannot be very helpful without more information.

Thanks
I'm gonna use agilent way for that .
Hope it work


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Have you worked out yet why we need more information in order to provide a good answer?

Which agilent schematic are you using? It's probable that it could be simplified for your purpose, it's also very likely that there will be some subtleties in any design that will provide flat variable gain from DC to 100MHz that aren't obvious.

[DimitriP]

You be not now a lot I found myself annoy

Jesus christ!!

[Jay_Diddy_B]

Hi,

If you have a DAC in your function generator, have you considered varying the reference voltage to the DAC?

This is a DC voltage and therefore much easier to deal with.

You can put a small DAC between the reference and the reference input to the main DAC to control amplitude.

Jay_Diddy_B

[Fungus]

If you have a DAC in your function generator

Does he? That's the first mystery...

[Mechatrommer]

in my country a VGC is about 15 US . in large scale it is expensive 

good luck! i have an amplifier, err an opamp as an output stage in my FG, in that price range, just an opamp, no variable control nada...

Here's a circuit I found on the web. I think it will do what you're looking for. All you need is a cheap potentiometer:

that was everything i need . thanks . plz don't hurt ur brain to much

good luck! on not hurting your brain putting that in your 100MHz FG for the masses...

[tggzzz]

If you have a DAC in your function generator

Does he? That's the first mystery...

We did eventually manage to squeeze a partial schematic out of him, and it showed a differential current source. So a DAC is a good guess.

[navidrct]

Hi,

If you have a DAC in your function generator, have you considered varying the reference voltage to the DAC?

This is a DC voltage and therefore much easier to deal with.

You can put a small DAC between the reference and the reference input to the main DAC to control amplitude.

Jay_Diddy_B

My DAC have feedback but our purpose now is that don't use that

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[navidrct]

If you have a DAC in your function generator

Does he? That's the first mystery...

We did eventually manage to squeeze a partial schematic out of him, and it showed a differential current source. So a DAC is a good guess.

I'm new in forum thing . Sorry
I'll do my best . Thanks

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[tggzzz]

I'm new in forum thing . Sorry
I'll do my best . Thanks

Making mistakes is inevitable; we all do it. As I taught my daughter, "let's make new mistakes".

Understanding and applying what's in https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/ is relevant to more thna this forum; it is valuable in alll aspects all of life.

[navidrct]

I'm new in forum thing . Sorry
I'll do my best . Thanks

Making mistakes is inevitable; we all do it. As I taught my daughter, "let's make new mistakes".

Understanding and applying what's in https://entertaininghacks.wordpress.com/library-2/good-questions-pique-our-interest-and-dont-waste-our-time-2/ is relevant to more thna this forum; it is valuable in alll aspects all of life.

Thanks

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[krish2487]

I am guessing he is not a native english speaker...


Therein is a part of the problem. This can be addressed


The other being, lack of clarity on what,how,why he wants help with...
This part will need a certain introspection on his part and clear framing of answers to those questions.
I, myself, am not a native english speaker and I find that writing down on a piece of paper helps me articulate better.
 

[tggzzz]

This part will need a certain introspection on his part and clear framing of answers to those questions.
I, myself, am not a native english speaker and I find that writing down on a piece of paper helps me articulate better.

I - as an English speaker - find that writing down the problem, approaches, solutions, unknowns helps me a very great deal. Often to the extent that I'm able to answer my own question without bothering other people.

Of course, it does help if you know what to write down, i.e. have a clue about how to approach problem definition and problem exploration and problem solving.

[krish2487]

Touche!! :-) critical thinking and problem solving abilities are the missing part of the equation. I just did not think of them first.

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[navidrct]

Let's create topic for that. [emoji1]
What feedback resistor do u suggest?

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