Input stage

Thoma HauC · May 22, 2004

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

Jim Thompson · May 22, 2004

On Sat, 22 May 2004 17:36:12 +0200, Thoma HauC <rf.eerf@xob.liame>
wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

480)460-2350 | |
| E-mail Address at Website Fax

James Meyer · May 22, 2004

On Sat, 22 May 2004 08:59:54 -0700, Jim Thompson <thegreatone@example.com>
posted this:

On Sat, 22 May 2004 17:36:12 +0200, Thoma HauC <rf.eerf@xob.liame
wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

What's an "input stage"?

...Jim Thompson

input stage........................first stage

output stage.......................last stage

intermediate stage.................any stage between the input and output stage

silver stage.......................the movies

Jim

John Larkin · May 22, 2004

On Sat, 22 May 2004 08:59:54 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On Sat, 22 May 2004 17:36:12 +0200, Thoma HauC <rf.eerf@xob.liame
wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

What's an "input stage"?

...Jim Thompson

200 MHz. Must be audio.

John

Reg Edwards · May 22, 2004

The lower the input signal the lower the distortion. Nothing to worry
about.

To obtain wide band up to 200 MHz use a low power, dual gate FET with a
drain load of one or two hundred ohms. So expect a very low stage gain. You
may have to use 2 or more stages for small signal levels. Keep stray
capacitance to its lowest possible level.

You are attempting the nearly impossible if you want anything to be flat up
to 200 MHz. Negative feedback and even lower stage gain MIGHT do the job.
----
Good luck with your search.

=====================================

Is there someone which could give me a link to a low distortion (-80dB)
and wide
band (200MHz) input stage ?

Tam/WB2TT · May 22, 2004

You might want to check out Minicircuits. Motorola also made modules like
that, but I don't know who would make these now. If not Mote, possibly ON or
Tyco. Communication Concepts and RF Parts used to sell these, plus various
Japanese ones.

Tam
"Thoma HauC" <rf.eerf@xob.liame> wrote in message
news:40af72b3$0$13927$636a15ce@news.free.fr...

Hello,

Is there someone which could give me a link to a low distortion (-80dB)
and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

John Larkin · May 22, 2004

On Sat, 22 May 2004 17:27:18 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

The lower the input signal the lower the distortion. Nothing to worry
about.

To obtain wide band up to 200 MHz use a low power, dual gate FET with a
drain load of one or two hundred ohms. So expect a very low stage gain. You
may have to use 2 or more stages for small signal levels. Keep stray
capacitance to its lowest possible level.

You are attempting the nearly impossible if you want anything to be flat up
to 200 MHz. Negative feedback and even lower stage gain MIGHT do the job.

Nowadays, there are opamps that will give plenty of low-distortion
gain to this frequency, or 10x this frequency even. And cheap MMICs
give numbers like 20 dB gain, 3 dB NF, and DC-5 GHz bandwidth.

Check TI and Analog Devices for screaming opamps. Sirenza or
Mini-Circuits for nice MMICs.

John

Fred Bloggs · May 22, 2004

John Larkin wrote:

On Sat, 22 May 2004 17:27:18 +0000 (UTC), "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:

The lower the input signal the lower the distortion. Nothing to worry
about.

To obtain wide band up to 200 MHz use a low power, dual gate FET with a
drain load of one or two hundred ohms. So expect a very low stage gain. You
may have to use 2 or more stages for small signal levels. Keep stray
capacitance to its lowest possible level.

You are attempting the nearly impossible if you want anything to be flat up
to 200 MHz. Negative feedback and even lower stage gain MIGHT do the job.

Nowadays, there are opamps that will give plenty of low-distortion
gain to this frequency, or 10x this frequency even. And cheap MMICs
give numbers like 20 dB gain, 3 dB NF, and DC-5 GHz bandwidth.

Check TI and Analog Devices for screaming opamps. Sirenza or
Mini-Circuits for nice MMICs.

John

You can't be serious! Maybe at unity gain and signal levels <30dBm...and
which distortion IP3 or IP2- not aware that THD is used at these
frequencies- geez wonder why....

John Larkin · May 22, 2004

On Sat, 22 May 2004 18:43:04 GMT, Fred Bloggs <nospam@nospam.com>
wrote:

John Larkin wrote:
On Sat, 22 May 2004 17:27:18 +0000 (UTC), "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:

The lower the input signal the lower the distortion. Nothing to worry
about.

To obtain wide band up to 200 MHz use a low power, dual gate FET with a
drain load of one or two hundred ohms. So expect a very low stage gain. You
may have to use 2 or more stages for small signal levels. Keep stray
capacitance to its lowest possible level.

You are attempting the nearly impossible if you want anything to be flat up
to 200 MHz. Negative feedback and even lower stage gain MIGHT do the job.

Nowadays, there are opamps that will give plenty of low-distortion
gain to this frequency, or 10x this frequency even. And cheap MMICs
give numbers like 20 dB gain, 3 dB NF, and DC-5 GHz bandwidth.

Check TI and Analog Devices for screaming opamps. Sirenza or
Mini-Circuits for nice MMICs.

John

You can't be serious! Maybe at unity gain and signal levels <30dBm...and
which distortion IP3 or IP2- not aware that THD is used at these
frequencies- geez wonder why....

Of course I'm serious. Opamp GBWs are now at 18 GHz, and cheap 50-ohm
darlington MMICs are up to 10 GHz. But the op's request is pretty
(well, very) vague, so we don't know what's important here. He did say
"input stage" so 30 dBm likely isn't called for, unless it's the input
stage for a big ole transmitter!

John

Reg Edwards · May 22, 2004

Nowadays, there are opamps that will give plenty of low-distortion
gain to this frequency, or 10x this frequency even. And cheap MMICs
give numbers like 20 dB gain, 3 dB NF, and DC-5 GHz bandwidth.

=====================

Agreed I'm out of date. But suppose he wants a medium to high input
impedance, as he is likely to want at 200 MHz.

John Larkin · May 22, 2004

On Sat, 22 May 2004 22:42:49 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

Nowadays, there are opamps that will give plenty of low-distortion
gain to this frequency, or 10x this frequency even. And cheap MMICs
give numbers like 20 dB gain, 3 dB NF, and DC-5 GHz bandwidth.

=====================

Agreed I'm out of date. But suppose he wants a medium to high input
impedance, as he is likely to want at 200 MHz.

An opamp will do that, fraction of a pF. But we don't know what he
wants.

John

Activ8 · May 23, 2004

On Sat, 22 May 2004 16:08:10 GMT, James Meyer wrote:

On Sat, 22 May 2004 08:59:54 -0700, Jim Thompson <thegreatone@example.com
posted this:

On Sat, 22 May 2004 17:36:12 +0200, Thoma HauC <rf.eerf@xob.liame
wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and wide
band (200MHz) input stage ?

Thank you in advance

Thoma

What's an "input stage"?

...Jim Thompson

input stage........................first stage

output stage.......................last stage

intermediate stage.................any stage between the input and output stage

silver stage.......................the movies

Jim

That's "silver screen".
--
Best Regards,
Mike

Thoma HauC · May 23, 2004

Thoma HauC wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB) and
wide band (200MHz) input stage ?

Thank you in advance

Thoma

After reading your answers, I realize that I was not very precise. The input
stage will consist of several scales (1/1 & 1/10). It will have to
present an impedance of 1 Mohms. What interests me, it is the structure in
order to have a low impedance output in the first stage. If I put a follower,
it will distort the signal.

Input impedance : 1 Momhs
Wide band : 200 MHz
Low distortion : 80 dB
Three scales : 1/1, 1/10
Maximum input voltage : 5 V

Thank you in advance

Thoma

Tam/WB2TT · May 23, 2004

"Thoma HauC" <rf.eerf@xob.liame> wrote in message
news:40b0d815$0$7710$636a15ce@news.free.fr...

Thoma HauC wrote:

Hello,

Is there someone which could give me a link to a low distortion (-80dB)
and
wide band (200MHz) input stage ?

Thank you in advance

Thoma

After reading your answers, I realize that I was not very precise. The
input
stage will consist of several scales (1/1, 1/10 & 1/100). It will have to
present an impedance of 1 Mohms. What interests me, it is the structure in
order to have a low impedance output in the first stage. If I put a
follower,
it will distort the signal.

Input impedance : 1 Momhs
Wide band : 200 MHz

I don't think there is a device in existance that has 1 Megaohm impedance at
200 MHz, not even a 1M reistor.

Tam

Low distortion : 80 dB
Three scales : 1/1, 1/10
Maximum input voltage : 5 V

Thank you in advance

Input stage

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