[SI-LIST] Re: 500 MHZ Squarewave (was (no subject))
- From: Fred Townsend <fred@xxxxxxxxxxxxx>
- To: kirti@xxxxxxxxxxxx
- Date: Wed, 23 Jul 2003 13:06:05 -0700
Kirti, I suspect you have not accurately stated your intentions or your
problem. For starters how are you viewing the signals? A 500 MHz sinewave may
be viewed with a 500 MHz bandwidth scope (although I don not recommend it). A
500 MHz squarewave requires a scope with at least 5 GHz bandwidth. In most
cases that will be a sampling scope since most ordinary scopes do not go that
high.
Second, you say you are feeding 10vpp into a TTL to ECL converter. Ouch! TTL
to ECL converters are designed to take a TTL 0 to 3v signal and convert it to
an ECL -1.8 to -0.9. Note the function is primary of a level shifter. It has
no real gain (Av=0.3). Putting 10vpp on the input could damage the device. The
chip needs well bypassed +5 volt and -5.2 volt supplies to workas well. Also
since TTL devices are not usually rated for 500 MHz the converters seldom
achieve this bandwidth either.
If you want to quickly convert convert a 10Vpp sinewave to a 10 Vpp squarewave
I would build a flip-flop from either DMOS or GaAs FETs. Trigger the FF from
the 10vpp sinewave coupled to the gate of one FET and capacitor couple the
output from the drain of opposite FET.
Fred Townsend
Kirti Barpande wrote:
> Hello! Everyboby,
> I am getting problem in converting a high frequency (around 500MHz) Sine
> wave (-ve peak -5.0v and +ve peak +5v) to square wave. Obviously we cann't
> use TTL buffers at this frequency. I tried with many TTL to ECL converter
> buffers fron ONsemiconductors but I could not get results. Has any one done
> such conversion? If so please let me know. Also inform me if you have any
> idea about fast comparators working above 500 MHz.
> Mrs. Kirti Barpande Phone - 91-731-2488054
> Scientific Officer 'F' Fax - 91-731-2488000
> Controls lab,
> Room no.114, ADL Building,
> Centre foe Advanced Technology,
> Indore,(M.P.),India. Pin 452013
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