Forums

Highly Linear ADC Driver Amplifier - need suggestions

Started by Darol Klawetter May 14, 2013
I'm currently researching the amplifier options for the output stage of a R=
F receiver I'm designing. This stage will have a single-ended output and wi=
ll drive an ADC that has a SFDR of 100 dB. Of course, I need a highly linea=
r amplifier to prevent washing out my ADC performance, but I don't want to =
use one with differential I/O, which is typically used to drive high-perfor=
mance ADCs. I would prefer something simple, like a gain block that would r=
educe my parts count. The frequency range of my output is 2 MHz to 50 MHz, =
which is too low for most RF gain blocks' optimal frequency range. My goal =
is to drive 2.5 vpp, while preventing distortion that kills the SFDR of my =
ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions?

Thanks,

Darol Klawetter
Darol Klawetter wrote:
> I'm currently researching the amplifier options for the output stage > of a RF receiver I'm designing. This stage will have a single-ended > output and will drive an ADC that has a SFDR of 100 dB. Of course, I > need a highly linear amplifier to prevent washing out my ADC > performance, but I don't want to use one with differential I/O, which > is typically used to drive high-performance ADCs. I would prefer > something simple, like a gain block that would reduce my parts count. > The frequency range of my output is 2 MHz to 50 MHz, which is too low > for most RF gain blocks' optimal frequency range. My goal is to drive > 2.5 vpp, while preventing distortion that kills the SFDR of my ADC. A > gain of 15 dB to 30 dB is acceptable. Any suggestions? >
AD603? http://www.analog.com/static/imported-files/data_sheets/AD603.pdf Then you can set the gain via a control voltage. These things are very good, I used them in ultrasound systems where signal integrity is very critical. Unfortunately they have become a bit expensive for my taste so I haven't used one in new designs in a while. -- Regards, Joerg http://www.analogconsultants.com/
On Tue, 14 May 2013 14:02:08 -0700, Darol Klawetter wrote:

> I'm currently researching the amplifier options for the output stage of > a RF receiver I'm designing. This stage will have a single-ended output > and will drive an ADC that has a SFDR of 100 dB. Of course, I need a > highly linear amplifier to prevent washing out my ADC performance, but I > don't want to use one with differential I/O, which is typically used to > drive high-performance ADCs. I would prefer something simple, like a > gain block that would reduce my parts count. The frequency range of my > output is 2 MHz to 50 MHz, which is too low for most RF gain blocks' > optimal frequency range. My goal is to drive 2.5 vpp, while preventing > distortion that kills the SFDR of my ADC. A gain of 15 dB to 30 dB is > acceptable. Any suggestions?
Use a balun into the ADC. MiniCircuits has 'em, possibly even at that low a frequency range. If not, wind your own or have it wound. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Tue, 14 May 2013 14:02:08 -0700 (PDT), Darol Klawetter
<darol.klawetter@gmail.com> wrote:

>I'm currently researching the amplifier options for the output stage of a RF receiver I'm designing. This stage will have a single-ended output and will drive an ADC that has a SFDR of 100 dB. Of course, I need a highly linear amplifier to prevent washing out my ADC performance, but I don't want to use one with differential I/O, which is typically used to drive high-performance ADCs. I would prefer something simple, like a gain block that would reduce my parts count. The frequency range of my output is 2 MHz to 50 MHz, which is too low for most RF gain blocks' optimal frequency range. My goal is to drive 2.5 vpp, while preventing distortion that kills the SFDR of my ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions? > >Thanks, > >Darol Klawetter
Most fast ADCs are differential-in, and have best linearity when driven differential. So one of the diff gadgets would be best. ADA4960-1 is outrageous. It could do se-to-diff if you need that. For single-ended, use a fast opamp like AD8009 or something. MMICS like ERA5 actually work well at low frequencies, single-ended or with maybe a balun as suggested. 30 dB at 50 MHz is a lot of GBW for a single stage. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
On Tuesday, May 14, 2013 5:02:08 PM UTC-4, Darol Klawetter wrote:
> I'm currently researching the amplifier options for the output stage of a=
RF receiver I'm designing. This stage will have a single-ended output and = will drive an ADC that has a SFDR of 100 dB. Of course, I need a highly lin= ear amplifier to prevent washing out my ADC performance, but I don't want t= o use one with differential I/O, which is typically used to drive high-perf= ormance ADCs. I would prefer something simple, like a gain block that would= reduce my parts count. The frequency range of my output is 2 MHz to 50 MHz= , which is too low for most RF gain blocks' optimal frequency range. My goa= l is to drive 2.5 vpp, while preventing distortion that kills the SFDR of m= y ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions?
>=20 >=20 >=20 > Thanks, >=20 >=20 >=20 > Darol Klawetter
Thanks for the suggestions. My ADC card (which is separate from my RF recei= ver card) already has a balun that is used to drive the diff input of the A= DC from a single-ended SMA input. I want to drive this single ended input w= ithout having to use a diff output driver into another balun. I'll do it if= necessary to get the performance I need, but I'm trying keep my parts coun= t down on receiver's output stage. Joerg, the AD603 has 60 dBc harmonic distortion.
On 15.5.13 7:02 , Darol Klawetter wrote:
> On Tuesday, May 14, 2013 5:02:08 PM UTC-4, Darol Klawetter wrote: >> I'm currently researching the amplifier options for the output stage of a RF receiver I'm designing. This stage will have a single-ended output and will drive an ADC that has a SFDR of 100 dB. Of course, I need a highly linear amplifier to prevent washing out my ADC performance, but I don't want to use one with differential I/O, which is typically used to drive high-performance ADCs. I would prefer something simple, like a gain block that would reduce my parts count. The frequency range of my output is 2 MHz to 50 MHz, which is too low for most RF gain blocks' optimal frequency range. My goal is to drive 2.5 vpp, while preventing distortion that kills the SFDR of my ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions? >> >> >> >> Thanks, >> >> >> >> Darol Klawetter > > Thanks for the suggestions. My ADC card (which is separate from my RF receiver card) already has a balun that is used to drive the diff input of the ADC from a single-ended SMA input. I want to drive this single ended input without having to use a diff output driver into another balun. I'll do it if necessary to get the performance I need, but I'm trying keep my parts count down on receiver's output stage. > > Joerg, the AD603 has 60 dBc harmonic distortion.
It seems to me that you're looking for a high dynamic-range HF front end amplifier. Whole volumes have been written about the subject. You should start with the ARRL Handbook and follow the leads (if you have not done so). I strongly suspect that you need to go to a discrete component design. The power levels needed to handle most of the HF range will be much for integrated designs. -- Tauno Voipio
No, I'm just looking for an acceptable single-ended driver for my IF output stage.
On Wed, 15 May 2013 21:16:49 +0300, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:

>On 15.5.13 7:02 , Darol Klawetter wrote: >> On Tuesday, May 14, 2013 5:02:08 PM UTC-4, Darol Klawetter wrote: >>> I'm currently researching the amplifier options for the output stage of a RF receiver I'm designing. This stage will have a single-ended output and will drive an ADC that has a SFDR of 100 dB. Of course, I need a highly linear amplifier to prevent washing out my ADC performance, but I don't want to use one with differential I/O, which is typically used to drive high-performance ADCs. I would prefer something simple, like a gain block that would reduce my parts count. The frequency range of my output is 2 MHz to 50 MHz, which is too low for most RF gain blocks' optimal frequency range. My goal is to drive 2.5 vpp, while preventing distortion that kills the SFDR of my ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions? >>> >>> >>> >>> Thanks, >>> >>> >>> >>> Darol Klawetter >> >> Thanks for the suggestions. My ADC card (which is separate from my RF receiver card) already has a balun that is used to drive the diff input of the ADC from a single-ended SMA input. I want to drive this single ended input without having to use a diff output driver into another balun. I'll do it if necessary to get the performance I need, but I'm trying keep my parts count down on receiver's output stage. >> >> Joerg, the AD603 has 60 dBc harmonic distortion. > > >It seems to me that you're looking for a high dynamic-range HF >front end amplifier. Whole volumes have been written about >the subject. You should start with the ARRL Handbook and >follow the leads (if you have not done so). > >I strongly suspect that you need to go to a discrete >component design. The power levels needed to handle most >of the HF range will be much for integrated designs.
There are lots of opamps that would work. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
On Wednesday, May 15, 2013 4:32:32 PM UTC-4, John Larkin wrote:
> On Wed, 15 May 2013 21:16:49 +0300, Tauno Voipio >=20 > <tauno.voipio@notused.fi.invalid> wrote: >=20 >=20 >=20 > >On 15.5.13 7:02 , Darol Klawetter wrote: >=20 > >> On Tuesday, May 14, 2013 5:02:08 PM UTC-4, Darol Klawetter wrote: >=20 > >>> I'm currently researching the amplifier options for the output stage =
of a RF receiver I'm designing. This stage will have a single-ended output = and will drive an ADC that has a SFDR of 100 dB. Of course, I need a highly= linear amplifier to prevent washing out my ADC performance, but I don't wa= nt to use one with differential I/O, which is typically used to drive high-= performance ADCs. I would prefer something simple, like a gain block that w= ould reduce my parts count. The frequency range of my output is 2 MHz to 50= MHz, which is too low for most RF gain blocks' optimal frequency range. My= goal is to drive 2.5 vpp, while preventing distortion that kills the SFDR = of my ADC. A gain of 15 dB to 30 dB is acceptable. Any suggestions?
>=20 > >>> >=20 > >>> >=20 > >>> >=20 > >>> Thanks, >=20 > >>> >=20 > >>> >=20 > >>> >=20 > >>> Darol Klawetter >=20 > >> >=20 > >> Thanks for the suggestions. My ADC card (which is separate from my RF =
receiver card) already has a balun that is used to drive the diff input of = the ADC from a single-ended SMA input. I want to drive this single ended in= put without having to use a diff output driver into another balun. I'll do = it if necessary to get the performance I need, but I'm trying keep my parts= count down on receiver's output stage.
>=20 > >> >=20 > >> Joerg, the AD603 has 60 dBc harmonic distortion. >=20 > > >=20 > > >=20 > >It seems to me that you're looking for a high dynamic-range HF >=20 > >front end amplifier. Whole volumes have been written about >=20 > >the subject. You should start with the ARRL Handbook and >=20 > >follow the leads (if you have not done so). >=20 > > >=20 > >I strongly suspect that you need to go to a discrete >=20 > >component design. The power levels needed to handle most >=20 > >of the HF range will be much for integrated designs. >=20 >=20 >=20 > There are lots of opamps that would work.=20 >=20 >=20 >=20 >=20 >=20 > --=20 >=20 >=20 >=20 > John Larkin Highland Technology, Inc >=20 >=20 >=20 > jlarkin at highlandtechnology dot com >=20 > http://www.highlandtechnology.com >=20 >=20 >=20 > Precision electronic instrumentation >=20 > Picosecond-resolution Digital Delay and Pulse generators >=20 > Custom laser drivers and controllers >=20 > Photonics and fiberoptic TTL data links >=20 > VME thermocouple, LVDT, synchro acquisition and simulation
Hmmm...maybe so, but I haven't found one with distortion products that are = lower than my ADC noise floor. Can I live with that? Probably, but I would = prefer to use an amp that doesn't degrade my ADC performance. Darol Klawetter
On Tue, 14 May 2013 14:02:08 -0700 (PDT), Darol Klawetter
<darol.klawetter@gmail.com> wrote:

>I'm currently researching the amplifier options for the output stage of =
a RF receiver I'm designing. This stage will have a single-ended output = and will drive an ADC that has a SFDR of 100 dB. Of course, I need a = highly linear amplifier to prevent washing out my ADC performance, but I = don't want to use one with differential I/O, which is typically used to = drive high-performance ADCs. I would prefer something simple, like a gain= block that would reduce my parts count. The frequency range of my output= is 2 MHz to 50 MHz, which is too low for most RF gain blocks' optimal = frequency range. My goal is to drive 2.5 vpp, while preventing distortion= that kills the SFDR of my ADC. A gain of 15 dB to 30 dB is acceptable. = Any suggestions?
> >Thanks, > >Darol Klawetter
Read the thread. Listen up, the high performance ADCs use differential for good reasons. Quit goofing around and go fully differential and dump the baluns. 100 dB is one heck of a range (about 26 bits), so whatever the converter cost figure on at least 20% of that for the input = amplifier, maybe even over 300% as much. If it is differential input then give it what it wants and is designed for. Then use really good layout or you = will waste all that capability. ?-)