really fast buffers

Started by John Larkin October 3, 2018
I'm designing a test board for a laser controller. Incoming signals,
fast 5 volt pulses, will need to get routed to scopes, counters, and
some other stuff. It will be kind a maze of connectors and traces and
probably relays; it's hard to beat a relay as a test path switch.

But life would be a lot better if I could fan out some of the signals
at their input connector. I want a zero-delay, zero-jitter buffer.
Under 1 ns delay might be a reasonable target, with very stable prop
delay.

Just resistors could work, but that loses amplitude, and the ends of
the fanout traces would have to be always terminated to avoid
reflections. Something unilateral would be easier.

Fast opamp? THS3201 maybe. I'll have to Spice the prop delay.

Some sort of source follower, bipolar or phemt or something?

ECL/Eclips gate? 10EP89 or something.

One of the screaming Analog Devices comparators?



CMOS parts are probably all too slow, and they have terrible delay
tempcos.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

torsdag den 4. oktober 2018 kl. 00.03.49 UTC+2 skrev John Larkin:
> I'm designing a test board for a laser controller. Incoming signals, > fast 5 volt pulses, will need to get routed to scopes, counters, and > some other stuff. It will be kind a maze of connectors and traces and > probably relays; it's hard to beat a relay as a test path switch. > > But life would be a lot better if I could fan out some of the signals > at their input connector. I want a zero-delay, zero-jitter buffer. > Under 1 ns delay might be a reasonable target, with very stable prop > delay. > > Just resistors could work, but that loses amplitude, and the ends of > the fanout traces would have to be always terminated to avoid > reflections. Something unilateral would be easier. > > Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. > > Some sort of source follower, bipolar or phemt or something? > > ECL/Eclips gate? 10EP89 or something. > > One of the screaming Analog Devices comparators? > > > > CMOS parts are probably all too slow, and they have terrible delay > tempcos. >
clock buffers ?
On Wed, 03 Oct 2018 15:03:38 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

>I'm designing a test board for a laser controller. Incoming signals, >fast 5 volt pulses, will need to get routed to scopes, counters, and >some other stuff. It will be kind a maze of connectors and traces and >probably relays; it's hard to beat a relay as a test path switch. > >But life would be a lot better if I could fan out some of the signals >at their input connector. I want a zero-delay, zero-jitter buffer. >Under 1 ns delay might be a reasonable target, with very stable prop >delay. > >Just resistors could work, but that loses amplitude, and the ends of >the fanout traces would have to be always terminated to avoid >reflections. Something unilateral would be easier. > >Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. > >Some sort of source follower, bipolar or phemt or something? > >ECL/Eclips gate? 10EP89 or something. > >One of the screaming Analog Devices comparators? > > > >CMOS parts are probably all too slow, and they have terrible delay >tempcos.
TI's BUF602 looks pretty good for this. It's designed to be a gain-of-one buffer. Weird pinout, not like an opamp. GBW is 1 GHZ, pretty good, but the slew rate is 8 v/ns. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Wednesday, October 3, 2018 at 6:52:28 PM UTC-4, John Larkin wrote:
> On Wed, 03 Oct 2018 15:03:38 -0700, John Larkin > <jjlarkin@highland_snip_technology.com> wrote: > > >I'm designing a test board for a laser controller. Incoming signals, > >fast 5 volt pulses, will need to get routed to scopes, counters, and > >some other stuff. It will be kind a maze of connectors and traces and > >probably relays; it's hard to beat a relay as a test path switch. > > > >But life would be a lot better if I could fan out some of the signals > >at their input connector. I want a zero-delay, zero-jitter buffer. > >Under 1 ns delay might be a reasonable target, with very stable prop > >delay. > > > >Just resistors could work, but that loses amplitude, and the ends of > >the fanout traces would have to be always terminated to avoid > >reflections. Something unilateral would be easier. > > > >Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. > > > >Some sort of source follower, bipolar or phemt or something? > > > >ECL/Eclips gate? 10EP89 or something. > > > >One of the screaming Analog Devices comparators? > > > > > > > >CMOS parts are probably all too slow, and they have terrible delay > >tempcos. > > TI's BUF602 looks pretty good for this. It's designed to be a > gain-of-one buffer. Weird pinout, not like an opamp. > > GBW is 1 GHZ, pretty good, but the slew rate is 8 v/ns.
8 v/ns is too slow? how much voltage do you need? (sorry I mostly live in 'audio' land, ~10 v/us.) George H.
> > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
On 10/03/2018 06:03 PM, John Larkin wrote:
> I'm designing a test board for a laser controller. Incoming signals, > fast 5 volt pulses, will need to get routed to scopes, counters, and > some other stuff. It will be kind a maze of connectors and traces and > probably relays; it's hard to beat a relay as a test path switch. > > But life would be a lot better if I could fan out some of the signals > at their input connector. I want a zero-delay, zero-jitter buffer. > Under 1 ns delay might be a reasonable target, with very stable prop > delay. > > Just resistors could work, but that loses amplitude, and the ends of > the fanout traces would have to be always terminated to avoid > reflections. Something unilateral would be easier. > > Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. > > Some sort of source follower, bipolar or phemt or something? > > ECL/Eclips gate? 10EP89 or something. > > One of the screaming Analog Devices comparators? > > > > CMOS parts are probably all too slow, and they have terrible delay > tempcos. > >
My intuition thinks to skip the op amp and CMOS gates and go directly for the source follower, maybe using like a phemt and fast bipolar or phemt and mosfet in a compound arrangement, will get there.
On Wed, 3 Oct 2018 18:08:33 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Wednesday, October 3, 2018 at 6:52:28 PM UTC-4, John Larkin wrote: >> On Wed, 03 Oct 2018 15:03:38 -0700, John Larkin >> <jjlarkin@highland_snip_technology.com> wrote: >> >> >I'm designing a test board for a laser controller. Incoming signals, >> >fast 5 volt pulses, will need to get routed to scopes, counters, and >> >some other stuff. It will be kind a maze of connectors and traces and >> >probably relays; it's hard to beat a relay as a test path switch. >> > >> >But life would be a lot better if I could fan out some of the signals >> >at their input connector. I want a zero-delay, zero-jitter buffer. >> >Under 1 ns delay might be a reasonable target, with very stable prop >> >delay. >> > >> >Just resistors could work, but that loses amplitude, and the ends of >> >the fanout traces would have to be always terminated to avoid >> >reflections. Something unilateral would be easier. >> > >> >Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. >> > >> >Some sort of source follower, bipolar or phemt or something? >> > >> >ECL/Eclips gate? 10EP89 or something. >> > >> >One of the screaming Analog Devices comparators? >> > >> > >> > >> >CMOS parts are probably all too slow, and they have terrible delay >> >tempcos. >> >> TI's BUF602 looks pretty good for this. It's designed to be a >> gain-of-one buffer. Weird pinout, not like an opamp. >> >> GBW is 1 GHZ, pretty good, but the slew rate is 8 v/ns. >8 v/ns is too slow? how much voltage do you need?
No, the 1 GHz is mediocre. The 8v/ns is great. I'll be following about a 4 volt logic swing from the DUT. This is a real analog buffer, so if I route the buffered signal to a scope I'll see pretty much what's there, not a digitally cleaned-up or attenuated version. I'm guessing it won't add much jitter.
>(sorry I mostly live in 'audio' land, ~10 v/us.)
How do you tolerate waiting around? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Wednesday, October 3, 2018 at 9:54:51 PM UTC-4, bitrex wrote:

> My intuition thinks to skip the op amp and CMOS gates and go directly > for the source follower, maybe using like a phemt and fast bipolar or > phemt and mosfet in a compound arrangement, will get there.
I'm with you on the follower, perhaps a 42GHz BFP650, $0.285CAD @QTY100 at Arrow: https://octopart.com/search?q=BFP650&oq=BFP650&start=0 How would you use these in a compound arrangement? (LTspice ASC wellcome for the schematic. I wouldn't expect it to run.)
On Wed, 3 Oct 2018 20:10:43 -0700 (PDT), Steve Wilson
<9fe142ac@gmail.com> wrote:

>On Wednesday, October 3, 2018 at 9:54:51 PM UTC-4, bitrex wrote: > >> My intuition thinks to skip the op amp and CMOS gates and go directly >> for the source follower, maybe using like a phemt and fast bipolar or >> phemt and mosfet in a compound arrangement, will get there. > >I'm with you on the follower, perhaps a 42GHz BFP650, $0.285CAD @QTY100 at Arrow: > >https://octopart.com/search?q=BFP650&oq=BFP650&start=0
That would work, as a couple or few emitter followers to fan out my incoming signal. It has decent beta at, say, 50 mA or even 100 mA (driving something like 5 volts into 50 ohms). The Vbe offset would be more predictable than the turn-on of a phemt. I'll be timing edges to picoseconds so I don't want unpredictable offsets.
> >How would you use these in a compound arrangement? (LTspice ASC wellcome for the
schematic. I wouldn't expect it to run.) You could servo out the Vbe offset with an opamp, but that would be a hassle to do lots of times on my board. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 03/10/2018 23:23, Lasse Langwadt Christensen wrote:
> torsdag den 4. oktober 2018 kl. 00.03.49 UTC+2 skrev John Larkin: >> I'm designing a test board for a laser controller. Incoming signals, >> fast 5 volt pulses, will need to get routed to scopes, counters, and >> some other stuff. It will be kind a maze of connectors and traces and >> probably relays; it's hard to beat a relay as a test path switch. >> >> But life would be a lot better if I could fan out some of the signals >> at their input connector. I want a zero-delay, zero-jitter buffer. >> Under 1 ns delay might be a reasonable target, with very stable prop >> delay. >> >> Just resistors could work, but that loses amplitude, and the ends of >> the fanout traces would have to be always terminated to avoid >> reflections. Something unilateral would be easier. >> >> Fast opamp? THS3201 maybe. I'll have to Spice the prop delay. >> >> Some sort of source follower, bipolar or phemt or something? >> >> ECL/Eclips gate? 10EP89 or something. >> >> One of the screaming Analog Devices comparators? >> >> >> >> CMOS parts are probably all too slow, and they have terrible delay >> tempcos. >> > > clock buffers ? >
All the low prop/zero prop clock buffers I know are PLL based and are no good for random signal buffering.
>>https://octopart.com/search?q=BFP650&oq=BFP650&start=0
>That would work, as a couple or few emitter followers to fan out my >incoming signal. It has decent beta at, say, 50 mA or even 100 mA >(driving something like 5 volts into 50 ohms).
>The Vbe offset would be more predictable than the turn-on of a phemt.
Their low drain impedances make pHEMTs very disappointing as followers, unless you bootstrap the drain. The late lamented ATF38148 could have a gain of 0.5 as a follower.
>I'll be timing edges to picoseconds so I don't want unpredictable
offsets. You'll need a base resistor to keep it from oscillating. Don't let anybody hang a cable on it. Cheers Phil Hobbs