On Wed, 07 Mar 2012 10:38:15 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 03/07/2012 10:27 AM, John Larkin wrote:
>> On Wed, 07 Mar 2012 10:21:09 -0500, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> On 09/07/2011 05:08 PM, John Larkin wrote:
>>>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> John Larkin wrote:
>>>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> John Larkin wrote:
>>>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Gents,
>>>>>>>>>>>
>>>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>>>>> and simulate in LTSpice.
>>>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>>>
>>>>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>>>> simple.
>>>>>>>>
>>>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>>>> there is a SPICE model.
>>>>>>>
>>>>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>>>>
>>>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>>>> curves!
>>>>>>>>>>
>>>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>>>>> but twice as big. No Spice model.
>>>>>>>>>>
>>>>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>>>> suitably negative.
>>>>>>>>>>
>>>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>>>
>>>>>>>>> That sounds like a white knuckle ride :-)
>>>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>>>
>>>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>>>
>>>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>>>
>>>>>> I have data!
>>>>>>
>>>>>
>>>>> Just one problem in my case: I found that even hotshot RF transistors
>>>>> take a noticeable time to get back out of even a slightly saturated
>>>>> condition. Nanoseconds, but still. The other issue is that you can't get
>>>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>>>> most of my cases because of a DC component that must not be disturbed.
>>>>
>>>> Pity. They do have a collector DC offset that is a function of base
>>>> current, a few 10s of millivolts typically.
>>>>
>>>> Sounds like you're designing a signal blanker, maybe?
>>>>
>>>> John
>>>>
>>>
>>> Upside down, their offset is lower.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> Oh, I measured the BFT25 reverse beta yesterday. On the ones we have
>> in stock, it's about 4. So I'll be using gaasfets to discharge my ramp
>> and switch the range caps.
>>
>> The fets are more expensive and need level shifters for their gate
>> drive, minor nuisances.
>>
>>
>Hmm. 16 did seem a bit high, but a factor of 4 error in BR doesn't give
>me much confidence in the model.
>
>Sure it wasn't oscillating? Diode-connected BFT25As want to do that
>when you get somewhere above 100 uA.
Not sure, but it's still set up (who cleans workbenches before another
problem comes up?) so I'll poke around a little more. But the reverse
beta increased from about 3 to about 4.5 smoothly as I went from
approximate saturation to a couple of volts e-b, so probably it's not
oscillation.
--
John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply by Phil Hobbs●March 7, 20122012-03-07
On 03/07/2012 10:27 AM, John Larkin wrote:
> On Wed, 07 Mar 2012 10:21:09 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 09/07/2011 05:08 PM, John Larkin wrote:
>>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>>> wrote:
>>>
>>>> John Larkin wrote:
>>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> John Larkin wrote:
>>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Gents,
>>>>>>>>>>
>>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>>>> and simulate in LTSpice.
>>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>>
>>>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>>> simple.
>>>>>>>
>>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>>> there is a SPICE model.
>>>>>>
>>>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>>>
>>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>>> curves!
>>>>>>>>>
>>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>>>> but twice as big. No Spice model.
>>>>>>>>>
>>>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>>> suitably negative.
>>>>>>>>>
>>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>>
>>>>>>>> That sounds like a white knuckle ride :-)
>>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>>
>>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>>
>>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>>
>>>>> I have data!
>>>>>
>>>>
>>>> Just one problem in my case: I found that even hotshot RF transistors
>>>> take a noticeable time to get back out of even a slightly saturated
>>>> condition. Nanoseconds, but still. The other issue is that you can't get
>>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>>> most of my cases because of a DC component that must not be disturbed.
>>>
>>> Pity. They do have a collector DC offset that is a function of base
>>> current, a few 10s of millivolts typically.
>>>
>>> Sounds like you're designing a signal blanker, maybe?
>>>
>>> John
>>>
>>
>> Upside down, their offset is lower.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Oh, I measured the BFT25 reverse beta yesterday. On the ones we have
> in stock, it's about 4. So I'll be using gaasfets to discharge my ramp
> and switch the range caps.
>
> The fets are more expensive and need level shifters for their gate
> drive, minor nuisances.
>
>
Hmm. 16 did seem a bit high, but a factor of 4 error in BR doesn't give
me much confidence in the model.
Sure it wasn't oscillating? Diode-connected BFT25As want to do that
when you get somewhere above 100 uA.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Reply by John Larkin●March 7, 20122012-03-07
On Wed, 07 Mar 2012 10:21:09 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 09/07/2011 05:08 PM, John Larkin wrote:
>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>> wrote:
>>
>>> John Larkin wrote:
>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> John Larkin wrote:
>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Gents,
>>>>>>>>>
>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>>> and simulate in LTSpice.
>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>
>>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>> simple.
>>>>>>
>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>> there is a SPICE model.
>>>>>
>>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>>
>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>> curves!
>>>>>>>>
>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>>> but twice as big. No Spice model.
>>>>>>>>
>>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>> suitably negative.
>>>>>>>>
>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>
>>>>>>> That sounds like a white knuckle ride :-)
>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>
>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>
>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>
>>>> I have data!
>>>>
>>>
>>> Just one problem in my case: I found that even hotshot RF transistors
>>> take a noticeable time to get back out of even a slightly saturated
>>> condition. Nanoseconds, but still. The other issue is that you can't get
>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>> most of my cases because of a DC component that must not be disturbed.
>>
>> Pity. They do have a collector DC offset that is a function of base
>> current, a few 10s of millivolts typically.
>>
>> Sounds like you're designing a signal blanker, maybe?
>>
>> John
>>
>
>Upside down, their offset is lower.
>
>Cheers
>
>Phil Hobbs
Oh, I measured the BFT25 reverse beta yesterday. On the ones we have
in stock, it's about 4. So I'll be using gaasfets to discharge my ramp
and switch the range caps.
The fets are more expensive and need level shifters for their gate
drive, minor nuisances.
--
John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply by Phil Hobbs●March 7, 20122012-03-07
On 09/07/2011 05:08 PM, John Larkin wrote:
> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
> wrote:
>
>> John Larkin wrote:
>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>> wrote:
>>>
>>>> John Larkin wrote:
>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Gents,
>>>>>>>>
>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>> and simulate in LTSpice.
>>>>>>> Have you asked NEC/CEL?
>>>>>>>
>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>> simple.
>>>>>
>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>> there is a SPICE model.
>>>>
>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>
>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>> curves!
>>>>>>>
>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>> but twice as big. No Spice model.
>>>>>>>
>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>> suitably negative.
>>>>>>>
>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>
>>>>>> That sounds like a white knuckle ride :-)
>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>
>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>
>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>> fraction of the price of PHEMT or DMOS discretes.
>>>
>>> I have data!
>>>
>>
>> Just one problem in my case: I found that even hotshot RF transistors
>> take a noticeable time to get back out of even a slightly saturated
>> condition. Nanoseconds, but still. The other issue is that you can't get
>> them to zip Vce to zero like a FET can with Vds. That is required in
>> most of my cases because of a DC component that must not be disturbed.
>
> Pity. They do have a collector DC offset that is a function of base
> current, a few 10s of millivolts typically.
>
> Sounds like you're designing a signal blanker, maybe?
>
> John
>
Upside down, their offset is lower.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Reply by Phil Hobbs●September 7, 20112011-09-07
On 09/07/2011 06:08 PM, Jamie wrote:
> Phil Hobbs wrote:
>
>> John Larkin wrote:
>>
>>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>>> wrote:
>>>
>>>> John Larkin wrote:
>>>>
>>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>
>>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> John Larkin wrote:
>>>>>>>>
>>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Gents,
>>>>>>>>>>
>>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509?
>>>>>>>>>> Or at
>>>>>>>>>> least one that's close enough for pulse stuff? CEL only has
>>>>>>>>>> the usual
>>>>>>>>>> microwave models but I want to use it as a fast low
>>>>>>>>>> capacitance switch
>>>>>>>>>> and simulate in LTSpice.
>>>>>>>>>
>>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>>
>>>>>>>> I haven't. Was in a rush and have plopped down a Calogic
>>>>>>>> DS-series part
>>>>>>>> because I know it can do the job in this case. But I'd like to
>>>>>>>> be able
>>>>>>>> to use the NE3509 in the future or in case things need to be
>>>>>>>> even faster.
>>>>>>>
>>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>>> simple.
>>>>>>>
>>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>>> there is a SPICE model.
>>>>>>
>>>>>> This is a very fast switching app where slopes and ringout
>>>>>> behavior matter.
>>>>>>
>>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>>> curves!
>>>>>>>>>
>>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves
>>>>>>>>> - and
>>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same
>>>>>>>>> thing
>>>>>>>>> but twice as big. No Spice model.
>>>>>>>>>
>>>>>>>>> They appear to behave like jfets, in that you can ground the
>>>>>>>>> source
>>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>>> suitably negative.
>>>>>>>>>
>>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>>
>>>>>>>> That sounds like a white knuckle ride :-)
>>>>>>>
>>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>>
>>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>>
>>>>>
>>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>>
>>>>> I have data!
>>>>>
>>>>
>>>> Just one problem in my case: I found that even hotshot RF transistors
>>>> take a noticeable time to get back out of even a slightly saturated
>>>> condition. Nanoseconds, but still. The other issue is that you can't
>>>> get
>>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>>> most of my cases because of a DC component that must not be disturbed.
>>>
>>>
>>> Pity. They do have a collector DC offset that is a function of base
>>> current, a few 10s of millivolts typically.
>>>
>>> Sounds like you're designing a signal blanker, maybe?
>>>
>>> John
>>>
>>
>> Do they work better upside down? Inverted transistors can be quicker
>> than the same one right way up, and V_CEsat is very low.
>>
>> Cheers
>>
>> Phil Hobbs
> I don't about that how ever, I've opened some RF modules that you
> wouldn't want to operate upside down due to a gel that just sits there
> with out any apparent support from the housing cover to hold it in
> place. I don't know how such a module could pass high G test up side down.
>
> Jamie
>
>
By "upside down", I mean inverted, i.e. forward bias CB, reverse bias
CE. You get a low beta and low breakdown voltage, but much lower
feedback and output capacitances and a really low V_CEsat.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Reply by Joerg●September 7, 20112011-09-07
John Larkin wrote:
> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg <invalid@invalid.invalid>
> wrote:
>
>> John Larkin wrote:
>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg <invalid@invalid.invalid>
>>> wrote:
>>>
>>>> John Larkin wrote:
>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg <invalid@invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg <invalid@invalid.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Gents,
>>>>>>>>
>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>> and simulate in LTSpice.
>>>>>>> Have you asked NEC/CEL?
>>>>>>>
>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>> simple.
>>>>>
>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>> there is a SPICE model.
>>>>
>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>
>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>> curves!
>>>>>>>
>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>> but twice as big. No Spice model.
>>>>>>>
>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>> suitably negative.
>>>>>>>
>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>
>>>>>> That sounds like a white knuckle ride :-)
>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>
>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>> fraction of the price of PHEMT or DMOS discretes.
>>>
>>> I have data!
>>>
>> Just one problem in my case: I found that even hotshot RF transistors
>> take a noticeable time to get back out of even a slightly saturated
>> condition. Nanoseconds, but still. The other issue is that you can't get
>> them to zip Vce to zero like a FET can with Vds. That is required in
>> most of my cases because of a DC component that must not be disturbed.
>
> Pity. They do have a collector DC offset that is a function of base
> current, a few 10s of millivolts typically.
>
> Sounds like you're designing a signal blanker, maybe?
>
This one was more of a fast clamp & DC-restore function. A residual
DC-offset would not be so cool. However, at least according to SPICE
it'll work with the older devices. We'll see when the board is done,
when the rubber meets the road :-)
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by John Larkin●September 7, 20112011-09-07
On Wed, 07 Sep 2011 17:10:53 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>John Larkin wrote:
>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>> wrote:
>>
>>> John Larkin wrote:
>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> John Larkin wrote:
>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Gents,
>>>>>>>>>
>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>>> and simulate in LTSpice.
>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>
>>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>> simple.
>>>>>>
>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>> there is a SPICE model.
>>>>>
>>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>>
>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>> curves!
>>>>>>>>
>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>>> but twice as big. No Spice model.
>>>>>>>>
>>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>> suitably negative.
>>>>>>>>
>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>
>>>>>>> That sounds like a white knuckle ride :-)
>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>
>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>
>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>
>>>> I have data!
>>>>
>>>
>>> Just one problem in my case: I found that even hotshot RF transistors
>>> take a noticeable time to get back out of even a slightly saturated
>>> condition. Nanoseconds, but still. The other issue is that you can't get
>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>> most of my cases because of a DC component that must not be disturbed.
>>
>> Pity. They do have a collector DC offset that is a function of base
>> current, a few 10s of millivolts typically.
>>
>> Sounds like you're designing a signal blanker, maybe?
>>
>> John
>>
>
>Do they work better upside down? Inverted transistors can be quicker
>than the same one right way up, and V_CEsat is very low.
>
>Cheers
>
>Phil Hobbs
That would be interesting to try. Capacitance would probably be
higher, but some tricky base drive impedance could fix that.
Upside-down transistors can be made to saturate at precisely zero
volts, or less than zero if you drive the base hard.
John
Reply by Jamie●September 7, 20112011-09-07
Phil Hobbs wrote:
> John Larkin wrote:
>
>> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
>> wrote:
>>
>>> John Larkin wrote:
>>>
>>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>
>>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> John Larkin wrote:
>>>>>>>
>>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Gents,
>>>>>>>>>
>>>>>>>>> Does anyone know where to find the SPICE model for the NE3509?
>>>>>>>>> Or at
>>>>>>>>> least one that's close enough for pulse stuff? CEL only has the
>>>>>>>>> usual
>>>>>>>>> microwave models but I want to use it as a fast low capacitance
>>>>>>>>> switch
>>>>>>>>> and simulate in LTSpice.
>>>>>>>>
>>>>>>>> Have you asked NEC/CEL?
>>>>>>>>
>>>>>>> I haven't. Was in a rush and have plopped down a Calogic
>>>>>>> DS-series part
>>>>>>> because I know it can do the job in this case. But I'd like to be
>>>>>>> able
>>>>>>> to use the NE3509 in the future or in case things need to be even
>>>>>>> faster.
>>>>>>
>>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>>> simple.
>>>>>>
>>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>>> there is a SPICE model.
>>>>>
>>>>> This is a very fast switching app where slopes and ringout behavior
>>>>> matter.
>>>>>
>>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>>> curves!
>>>>>>>>
>>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves
>>>>>>>> - and
>>>>>>>> I'll email you what I have. Some of my data is for NE3508, same
>>>>>>>> thing
>>>>>>>> but twice as big. No Spice model.
>>>>>>>>
>>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>>> suitably negative.
>>>>>>>>
>>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>>
>>>>>>> That sounds like a white knuckle ride :-)
>>>>>>
>>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>>
>>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>>
>>>>
>>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>>> fraction of the price of PHEMT or DMOS discretes.
>>>>
>>>> I have data!
>>>>
>>>
>>> Just one problem in my case: I found that even hotshot RF transistors
>>> take a noticeable time to get back out of even a slightly saturated
>>> condition. Nanoseconds, but still. The other issue is that you can't get
>>> them to zip Vce to zero like a FET can with Vds. That is required in
>>> most of my cases because of a DC component that must not be disturbed.
>>
>>
>> Pity. They do have a collector DC offset that is a function of base
>> current, a few 10s of millivolts typically.
>>
>> Sounds like you're designing a signal blanker, maybe?
>>
>> John
>>
>
> Do they work better upside down? Inverted transistors can be quicker
> than the same one right way up, and V_CEsat is very low.
>
> Cheers
>
> Phil Hobbs
I don't about that how ever, I've opened some RF modules that you
wouldn't want to operate upside down due to a gel that just sits there
with out any apparent support from the housing cover to hold it in
place. I don't know how such a module could pass high G test up side down.
Jamie
Reply by Phil Hobbs●September 7, 20112011-09-07
John Larkin wrote:
> On Wed, 07 Sep 2011 11:24:25 -0700, Joerg<invalid@invalid.invalid>
> wrote:
>
>> John Larkin wrote:
>>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg<invalid@invalid.invalid>
>>> wrote:
>>>
>>>> John Larkin wrote:
>>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg<invalid@invalid.invalid>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg<invalid@invalid.invalid>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Gents,
>>>>>>>>
>>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>>> and simulate in LTSpice.
>>>>>>> Have you asked NEC/CEL?
>>>>>>>
>>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>>> Do you need a Spice model? As switches, these things are pretty
>>>>> simple.
>>>>>
>>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>>> enough for this application. There is a 2nd source (well, sorta) and
>>>> there is a SPICE model.
>>>>
>>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>>
>>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>>> curves!
>>>>>>>
>>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>>> but twice as big. No Spice model.
>>>>>>>
>>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>>> suitably negative.
>>>>>>>
>>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>>
>>>>>> That sounds like a white knuckle ride :-)
>>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>>
>>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>>
>>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>>> to use in shunt mode, with the emitter grounded, of course. They are a
>>> fraction of the price of PHEMT or DMOS discretes.
>>>
>>> I have data!
>>>
>>
>> Just one problem in my case: I found that even hotshot RF transistors
>> take a noticeable time to get back out of even a slightly saturated
>> condition. Nanoseconds, but still. The other issue is that you can't get
>> them to zip Vce to zero like a FET can with Vds. That is required in
>> most of my cases because of a DC component that must not be disturbed.
>
> Pity. They do have a collector DC offset that is a function of base
> current, a few 10s of millivolts typically.
>
> Sounds like you're designing a signal blanker, maybe?
>
> John
>
Do they work better upside down? Inverted transistors can be quicker
than the same one right way up, and V_CEsat is very low.
Cheers
Phil Hobbs
Reply by John Larkin●September 7, 20112011-09-07
On Wed, 07 Sep 2011 11:24:25 -0700, Joerg <invalid@invalid.invalid>
wrote:
>John Larkin wrote:
>> On Tue, 06 Sep 2011 17:53:22 -0700, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> John Larkin wrote:
>>>> On Tue, 06 Sep 2011 13:59:38 -0700, Joerg <invalid@invalid.invalid>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Tue, 06 Sep 2011 12:16:12 -0700, Joerg <invalid@invalid.invalid>
>>>>>> wrote:
>>>>>>
>>>>>>> Gents,
>>>>>>>
>>>>>>> Does anyone know where to find the SPICE model for the NE3509? Or at
>>>>>>> least one that's close enough for pulse stuff? CEL only has the usual
>>>>>>> microwave models but I want to use it as a fast low capacitance switch
>>>>>>> and simulate in LTSpice.
>>>>>> Have you asked NEC/CEL?
>>>>>>
>>>>> I haven't. Was in a rush and have plopped down a Calogic DS-series part
>>>>> because I know it can do the job in this case. But I'd like to be able
>>>>> to use the NE3509 in the future or in case things need to be even faster.
>>>> Do you need a Spice model? As switches, these things are pretty
>>>> simple.
>>>>
>>> Yes, I do need a model. Reason is that things like Cgd versus channel
>>> resistance matter. I was in a hurry so used Calogic parts now, good
>>> enough for this application. There is a 2nd source (well, sorta) and
>>> there is a SPICE model.
>>>
>>> This is a very fast switching app where slopes and ringout behavior matter.
>>>
>>>>>> The datasheets aren't bad, for an RF phemt. There are actual DC
>>>>>> curves!
>>>>>>
>>>>>> We use them as fast switches, and I took a bunch of data -
>>>>>> capacitances, Ron at various biases, tempco, extended DC curves - and
>>>>>> I'll email you what I have. Some of my data is for NE3508, same thing
>>>>>> but twice as big. No Spice model.
>>>>>>
>>>>>> They appear to behave like jfets, in that you can ground the source
>>>>>> and have the drain swing negative so long as you keep the gate
>>>>>> suitably negative.
>>>>>>
>>>>>> They also enhance to many times the zero-gate-voltage conductance,
>>>>>> numbers like 4 and 2 ohms Rds-on for the respective parts.
>>>>>>
>>>>> That sounds like a white knuckle ride :-)
>>>> No, just bias the gate a few tenth of a volt positive. Works great.
>>>>
>>> Ok, I'd dare to go to 300mV. But any closer is scary.
>>
>> One other thought: a BFT25 makes an interesting RF switch. It's easier
>> to use in shunt mode, with the emitter grounded, of course. They are a
>> fraction of the price of PHEMT or DMOS discretes.
>>
>> I have data!
>>
>
>Just one problem in my case: I found that even hotshot RF transistors
>take a noticeable time to get back out of even a slightly saturated
>condition. Nanoseconds, but still. The other issue is that you can't get
>them to zip Vce to zero like a FET can with Vds. That is required in
>most of my cases because of a DC component that must not be disturbed.
Pity. They do have a collector DC offset that is a function of base
current, a few 10s of millivolts typically.
Sounds like you're designing a signal blanker, maybe?
John