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 ?