Reply by Phil Hobbs ●May 12, 20212021-05-12
Simon S Aysdie wrote:

> On Sunday, May 9, 2021 at 10:49:03 AM UTC-7,
> jla...@highlandsniptechnology.com wrote:
>> On Sat, 8 May 2021 17:35:50 -0700 (PDT), Simon S Aysdie 
>> <gwh...@ti.com> wrote:
>> 
>>> On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote:
>>>> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie 
>>>> <gwh...@ti.com> wrote:
>>>> 
>>>>> On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin
>>>>> wrote:
>>>>>> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
>>>>>> <gwh...@ti.com> wrote:
>>>>>> 
>>>>>>> On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John
>>>>>>> Larkin wrote:
>>>>>>>> A few people make digital caps. This one is nice:
>>>>>>>> 
>>>>>>>> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D
>>>>>>>>
>>>>>>>>
>>>>>>>> 

I'm upgrading an oldish product that used a Maxim part that is, of

>>>>>>>> course, discontinued. Maxim won't even acknowledge the
>>>>>>>> old part number. Nobody in the world seems to have
>>>>>>>> any.
>>>>>>>> 
>>>>>>>> The Ixys part has three cap groups, coarse/medium/fine,
>>>>>>>> with 10 bits total. The transfer function code to
>>>>>>>> capacitance is sawtooth shaped, not monotonic, which
>>>>>>>> guarantees that any cap value in the full range has
>>>>>>>> some code that will hit it within one LSB.
>>>>>>>> 
>>>>>>>> I'm coarse tuning an LC oscillator at powerup, to be
>>>>>>>> close to 50 MHz, so that a varicap can take over and
>>>>>>>> swing it to exactly 50.
>>>>>>> 
>>>>>>> That's a neat looking part. Thanks.
>>>>>>> 
>>>>>>> Peregrine also makes them. I have never had cause to use
>>>>>>> them. None of them do what the Ixys part does, but the
>>>>>>> option for series capacitance is there. 
>>>>>>> https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs
>>>>>>
>>>>>>> 

They do want RF- to be grounded. That's not very clear.

>>>>>> 
>>>>>> I wonder why is has a min frequency rating of 100 MHz?
>>>>> 
>>>>> Dunno. Maybe a similar reason to the Peregrine Si on Sapphire
>>>>> switch's power rating that dives below 10 MHz.
>>>> MiniCircuits has two very similar Phemts. One is specified for
>>>> 0.45 to 6 GHz, and the other for 0.045 to 6 GHz. They both work
>>>> fine at real DC; I use them as switches.
>>>> 
>>>> Microwave people have weird ideas what they mean by "DC".
>>> 
>>> DC is under 1 GHz. :)
>>> 
>>>> I bought some absorptive RF switch ic's rated for DC-10 GHz,
>>>> that didn't work below 100 MHz. Hittite I recall.
>>>> 
>>>> Most "DC-to-xxGHz" rated microwave parts require input and
>>>> output signal coupling capacitors.
>>> 
>>> In that case "DC" means there are no internal DC blocks IN or
>>> OUT. So, that means it will go as low as the DC blocks you put in
>>> allow it to go. I am more annoyed by the opposite: when it has no
>>> internal DC blocks yet they say it only goes down 50 MHz or so.
>>> 
>>> A "DC" MMIC really does go down to DC. You just may not like the
>>> built-in offsets. hah hah
>>> 
>> A few honest people say LF instead of DC.
> 
> By that logic, any transistor or Darlington should come with a low
> frequency rating.
> 
> The limit is in what you attach to it, not the device itself. That's
> what they are telling you, and it is true, when they say "DC."
> 


RF folks also care about impedance matching, which is typically quite 
different near DC.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
Reply by John Larkin ●May 11, 20212021-05-11
On Tue, 11 May 2021 01:11:57 +0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:


>John Larkin <jlarkin@highland_atwork_technology.com> wrote in 
>news:mtlj9gda07sa2i1botgr4nga978cp6u8ug@4ax.com:
>
>> Well, RF people are not logical people.
>> 
>
>  Oh boy!  Yet another Larkin totally retarded crack.
>
>  Someone should stick a 10kW antenna up your ass and key up the mic 
>for an hour.  Fool modulation.
>
>  Just like Mountain Dew...  It'll tickle your innards!



It was a pun. Lighten up.
Reply by ●May 10, 20212021-05-10
John Larkin <jlarkin@highland_atwork_technology.com> wrote in 
news:mtlj9gda07sa2i1botgr4nga978cp6u8ug@4ax.com:


> Well, RF people are not logical people.
> 


  Oh boy!  Yet another Larkin totally retarded crack.

  Someone should stick a 10kW antenna up your ass and key up the mic 
for an hour.  Fool modulation.

  Just like Mountain Dew...  It'll tickle your innards!
Reply by John Larkin ●May 10, 20212021-05-10
On Mon, 10 May 2021 17:24:53 -0700 (PDT), Simon S Aysdie
<gwhite@ti.com> wrote:


>On Sunday, May 9, 2021 at 10:49:03 AM UTC-7, jla...@highlandsniptechnology.com wrote:
>> On Sat, 8 May 2021 17:35:50 -0700 (PDT), Simon S Aysdie
>> <gwh...@ti.com> wrote: 
>> 
>> >On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote: 
>> >> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie 
>> >> <gwh...@ti.com> wrote: 
>> >> 
>> >> >On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote: 
>> >> >> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
>> >> >> <gwh...@ti.com> wrote: 
>> >> >> 
>> >> >> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
>> >> >> >> A few people make digital caps. This one is nice: 
>> >> >> >> 
>> >> >> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
>> >> >> >> 
>> >> >> >> I'm upgrading an oldish product that used a Maxim part that is, of 
>> >> >> >> course, discontinued. Maxim won't even acknowledge the old part 
>> >> >> >> number. Nobody in the world seems to have any. 
>> >> >> >> 
>> >> >> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
>> >> >> >> total. The transfer function code to capacitance is sawtooth shaped, 
>> >> >> >> not monotonic, which guarantees that any cap value in the full range 
>> >> >> >> has some code that will hit it within one LSB. 
>> >> >> >> 
>> >> >> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
>> >> >> >> so that a varicap can take over and swing it to exactly 50. 
>> >> >> > 
>> >> >> >That's a neat looking part. Thanks. 
>> >> >> > 
>> >> >> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
>> >> >> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs 
>> >> >> They do want RF- to be grounded. That's not very clear. 
>> >> >> 
>> >> >> I wonder why is has a min frequency rating of 100 MHz? 
>> >> > 
>> >> >Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz. 
>> >> MiniCircuits has two very similar Phemts. One is specified for 0.45 to 
>> >> 6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real 
>> >> DC; I use them as switches. 
>> >> 
>> >> Microwave people have weird ideas what they mean by "DC". 
>> > 
>> >DC is under 1 GHz. :) 
>> > 
>> >> I bought 
>> >> some absorptive RF switch ic's rated for DC-10 GHz, that didn't work 
>> >> below 100 MHz. Hittite I recall. 
>> >> 
>> >> Most "DC-to-xxGHz" rated microwave parts require input and output 
>> >> signal coupling capacitors. 
>> > 
>> >In that case "DC" means there are no internal DC blocks IN or OUT. So, that means it will go as low as the DC blocks you put in allow it to go. I am more annoyed by the opposite: when it has no internal DC blocks yet they say it only goes down 50 MHz or so. 
>> > 
>> >A "DC" MMIC really does go down to DC. You just may not like the built-in offsets. hah hah 
>> >
>> A few honest people say LF instead of DC.
>
>By that logic, any transistor or Darlington should come with a low frequency rating.
>
>The limit is in what you attach to it, not the device itself. That's what they are telling you, and it is true, when they say "DC."


Well, RF people are not logical people.
Reply by Simon S Aysdie ●May 10, 20212021-05-10
On Sunday, May 9, 2021 at 10:49:03 AM UTC-7, jla...@highlandsniptechnology.com wrote:

> On Sat, 8 May 2021 17:35:50 -0700 (PDT), Simon S Aysdie
> <gwh...@ti.com> wrote: 
> 
> >On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote: 
> >> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie 
> >> <gwh...@ti.com> wrote: 
> >> 
> >> >On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote: 
> >> >> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
> >> >> <gwh...@ti.com> wrote: 
> >> >> 
> >> >> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
> >> >> >> A few people make digital caps. This one is nice: 
> >> >> >> 
> >> >> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
> >> >> >> 
> >> >> >> I'm upgrading an oldish product that used a Maxim part that is, of 
> >> >> >> course, discontinued. Maxim won't even acknowledge the old part 
> >> >> >> number. Nobody in the world seems to have any. 
> >> >> >> 
> >> >> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
> >> >> >> total. The transfer function code to capacitance is sawtooth shaped, 
> >> >> >> not monotonic, which guarantees that any cap value in the full range 
> >> >> >> has some code that will hit it within one LSB. 
> >> >> >> 
> >> >> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
> >> >> >> so that a varicap can take over and swing it to exactly 50. 
> >> >> > 
> >> >> >That's a neat looking part. Thanks. 
> >> >> > 
> >> >> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
> >> >> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs 
> >> >> They do want RF- to be grounded. That's not very clear. 
> >> >> 
> >> >> I wonder why is has a min frequency rating of 100 MHz? 
> >> > 
> >> >Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz. 
> >> MiniCircuits has two very similar Phemts. One is specified for 0.45 to 
> >> 6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real 
> >> DC; I use them as switches. 
> >> 
> >> Microwave people have weird ideas what they mean by "DC". 
> > 
> >DC is under 1 GHz. :) 
> > 
> >> I bought 
> >> some absorptive RF switch ic's rated for DC-10 GHz, that didn't work 
> >> below 100 MHz. Hittite I recall. 
> >> 
> >> Most "DC-to-xxGHz" rated microwave parts require input and output 
> >> signal coupling capacitors. 
> > 
> >In that case "DC" means there are no internal DC blocks IN or OUT. So, that means it will go as low as the DC blocks you put in allow it to go. I am more annoyed by the opposite: when it has no internal DC blocks yet they say it only goes down 50 MHz or so. 
> > 
> >A "DC" MMIC really does go down to DC. You just may not like the built-in offsets. hah hah 
> >
> A few honest people say LF instead of DC.


By that logic, any transistor or Darlington should come with a low frequency rating.

The limit is in what you attach to it, not the device itself. That's what they are telling you, and it is true, when they say "DC."
Reply by Reinhardt Behm ●May 10, 20212021-05-10
On 5/9/21 8:35 AM, Simon S Aysdie wrote:

>> Microwave people have weird ideas what they mean by "DC".
> DC is under 1 GHz.:)
> 

Slowly varying.

-- 
Reinhardt
Reply by ●May 9, 20212021-05-09
On Sat, 8 May 2021 17:35:50 -0700 (PDT), Simon S Aysdie
<gwhite@ti.com> wrote:


>On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote:
>> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie
>> <gwh...@ti.com> wrote: 
>> 
>> >On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote: 
>> >> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
>> >> <gwh...@ti.com> wrote: 
>> >> 
>> >> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
>> >> >> A few people make digital caps. This one is nice: 
>> >> >> 
>> >> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
>> >> >> 
>> >> >> I'm upgrading an oldish product that used a Maxim part that is, of 
>> >> >> course, discontinued. Maxim won't even acknowledge the old part 
>> >> >> number. Nobody in the world seems to have any. 
>> >> >> 
>> >> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
>> >> >> total. The transfer function code to capacitance is sawtooth shaped, 
>> >> >> not monotonic, which guarantees that any cap value in the full range 
>> >> >> has some code that will hit it within one LSB. 
>> >> >> 
>> >> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
>> >> >> so that a varicap can take over and swing it to exactly 50. 
>> >> > 
>> >> >That's a neat looking part. Thanks. 
>> >> > 
>> >> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
>> >> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs 
>> >> They do want RF- to be grounded. That's not very clear. 
>> >> 
>> >> I wonder why is has a min frequency rating of 100 MHz? 
>> > 
>> >Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz.
>> MiniCircuits has two very similar Phemts. One is specified for 0.45 to 
>> 6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real 
>> DC; I use them as switches. 
>> 
>> Microwave people have weird ideas what they mean by "DC". 
>
>DC is under 1 GHz. :)
>
>> I bought 
>> some absorptive RF switch ic's rated for DC-10 GHz, that didn't work 
>> below 100 MHz. Hittite I recall. 
>> 
>> Most "DC-to-xxGHz" rated microwave parts require input and output 
>> signal coupling capacitors.
>
>In that case "DC" means there are no internal DC blocks IN or OUT. So, that means it will go as low as the DC blocks you put in allow it to go. I am more annoyed by the opposite: when it has no internal DC blocks yet they say it only goes down 50 MHz or so.
>
>A "DC" MMIC really does go down to DC. You just may not like the built-in offsets. hah hah
> 


A few honest people say  LF  instead of DC.



-- 

John Larkin      Highland Technology, Inc

The best designs are necessarily accidental.
Reply by Joe Gwinn ●May 9, 20212021-05-09
On Sat, 8 May 2021 17:35:50 -0700 (PDT), Simon S Aysdie
<gwhite@ti.com> wrote:


>On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote:
>> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie
>> <gwh...@ti.com> wrote: 
>> 
>> >On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote: 
>> >> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
>> >> <gwh...@ti.com> wrote: 
>> >> 
>> >> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
>> >> >> A few people make digital caps. This one is nice: 
>> >> >> 
>> >> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
>> >> >> 
>> >> >> I'm upgrading an oldish product that used a Maxim part that is, of 
>> >> >> course, discontinued. Maxim won't even acknowledge the old part 
>> >> >> number. Nobody in the world seems to have any. 
>> >> >> 
>> >> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
>> >> >> total. The transfer function code to capacitance is sawtooth shaped, 
>> >> >> not monotonic, which guarantees that any cap value in the full range 
>> >> >> has some code that will hit it within one LSB. 
>> >> >> 
>> >> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
>> >> >> so that a varicap can take over and swing it to exactly 50. 
>> >> > 
>> >> >That's a neat looking part. Thanks. 
>> >> > 
>> >> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
>> >> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs 
>> >> They do want RF- to be grounded. That's not very clear. 
>> >> 
>> >> I wonder why is has a min frequency rating of 100 MHz? 
>> > 
>> >Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz.
>> MiniCircuits has two very similar Phemts. One is specified for 0.45 to 
>> 6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real 
>> DC; I use them as switches. 
>> 
>> Microwave people have weird ideas what they mean by "DC". 
>
>DC is under 1 GHz. :)
>
>> I bought 
>> some absorptive RF switch ic's rated for DC-10 GHz, that didn't work 
>> below 100 MHz. Hittite I recall. 
>> 
>> Most "DC-to-xxGHz" rated microwave parts require input and output 
>> signal coupling capacitors.
>
>In that case "DC" means there are no internal DC blocks IN or OUT. So, that means it will go as low as the DC blocks you put in allow it to go. I am more annoyed by the opposite: when it has no internal DC blocks yet they say it only goes down 50 MHz or so.
>
>A "DC" MMIC really does go down to DC. You just may not like the built-in offsets. hah hah
> 


Where then is the audio range?

Joe Gwinn
Reply by Simon S Aysdie ●May 8, 20212021-05-08
On Friday, May 7, 2021 at 2:47:47 PM UTC-7, John Larkin wrote:

> On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie
> <gwh...@ti.com> wrote: 
> 
> >On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote: 
> >> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
> >> <gwh...@ti.com> wrote: 
> >> 
> >> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
> >> >> A few people make digital caps. This one is nice: 
> >> >> 
> >> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
> >> >> 
> >> >> I'm upgrading an oldish product that used a Maxim part that is, of 
> >> >> course, discontinued. Maxim won't even acknowledge the old part 
> >> >> number. Nobody in the world seems to have any. 
> >> >> 
> >> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
> >> >> total. The transfer function code to capacitance is sawtooth shaped, 
> >> >> not monotonic, which guarantees that any cap value in the full range 
> >> >> has some code that will hit it within one LSB. 
> >> >> 
> >> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
> >> >> so that a varicap can take over and swing it to exactly 50. 
> >> > 
> >> >That's a neat looking part. Thanks. 
> >> > 
> >> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
> >> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs 
> >> They do want RF- to be grounded. That's not very clear. 
> >> 
> >> I wonder why is has a min frequency rating of 100 MHz? 
> > 
> >Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz.
> MiniCircuits has two very similar Phemts. One is specified for 0.45 to 
> 6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real 
> DC; I use them as switches. 
> 
> Microwave people have weird ideas what they mean by "DC". 


DC is under 1 GHz. :)


> I bought 
> some absorptive RF switch ic's rated for DC-10 GHz, that didn't work 
> below 100 MHz. Hittite I recall. 
> 
> Most "DC-to-xxGHz" rated microwave parts require input and output 
> signal coupling capacitors.


In that case "DC" means there are no internal DC blocks IN or OUT. So, that means it will go as low as the DC blocks you put in allow it to go. I am more annoyed by the opposite: when it has no internal DC blocks yet they say it only goes down 50 MHz or so.

A "DC" MMIC really does go down to DC. You just may not like the built-in offsets. hah hah
Reply by John Larkin ●May 7, 20212021-05-07
On Fri, 7 May 2021 14:09:34 -0700 (PDT), Simon S Aysdie
<gwhite@ti.com> wrote:


>On Friday, May 7, 2021 at 11:16:34 AM UTC-7, John Larkin wrote:
>> On Fri, 7 May 2021 10:13:48 -0700 (PDT), Simon S Aysdie 
>> <gwh...@ti.com> wrote: 
>> 
>> >On Thursday, April 15, 2021 at 5:46:05 PM UTC-7, John Larkin wrote: 
>> >> A few people make digital caps. This one is nice: 
>> >> 
>> >> https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/NCD2100TTR?qs=npTsUczJOtNXvd3UFPIV7g%3D%3D 
>> >> 
>> >> I'm upgrading an oldish product that used a Maxim part that is, of 
>> >> course, discontinued. Maxim won't even acknowledge the old part 
>> >> number. Nobody in the world seems to have any. 
>> >> 
>> >> The Ixys part has three cap groups, coarse/medium/fine, with 10 bits 
>> >> total. The transfer function code to capacitance is sawtooth shaped, 
>> >> not monotonic, which guarantees that any cap value in the full range 
>> >> has some code that will hit it within one LSB. 
>> >> 
>> >> I'm coarse tuning an LC oscillator at powerup, to be close to 50 MHz, 
>> >> so that a varicap can take over and swing it to exactly 50. 
>> > 
>> >That's a neat looking part. Thanks. 
>> > 
>> >Peregrine also makes them. I have never had cause to use them. None of them do what the Ixys part does, but the option for series capacitance is there. 
>> >https://www.psemi.com/products/family/rf-phase-amplitude-control/digital-tunable-capacitors-dtcs
>> They do want RF- to be grounded. That's not very clear. 
>> 
>> I wonder why is has a min frequency rating of 100 MHz?
>
>Dunno. Maybe a similar reason to the Peregrine Si on Sapphire switch's power rating that dives below 10 MHz.


MiniCircuits has two very similar Phemts. One is specified for 0.45 to
6 GHz, and the other for 0.045 to 6 GHz. They both work fine at real
DC; I use them as switches.

Microwave people have weird ideas what they mean by "DC". I bought
some absorptive RF switch ic's rated for DC-10 GHz, that didn't work
below 100 MHz. Hittite I recall. 

Most "DC-to-xxGHz" rated microwave parts require input and output
signal coupling capacitors.