[time-nuts] Modified Extron DA [WAS: Rb video]

Bob Camp lists at rtty.us
Fri Aug 9 16:57:34 EDT 2013


Hi

I still think that a distribution amp based on logic ic's is cheaper / simpler / lower power / higher performance. A pair of NC7SZ125's will dump 20 dbm into 50 ohms all day long running at 5.5 volts. Good isolation as well. Do the lowpass filter right and the harmonics are not an issue. Two coils / one cap plus dc blocking does it quite nicely. 

Bob

On Aug 9, 2013, at 4:44 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:

> Bob wrote:
> 
>> The original design with 3x75 ohm outputs would be driving a 50 ohm load rather than a 33 1/3 ohm load. That would put it "in spec" for the CLC409 as opposed to just out of spec current limit wise.
> 
> Right.  Analog video generally ranges from 0 to +1 V, so as a DC-coupled video amp the peak current into 3x75 ohm loads would be +40/-0 mA.  Very comfortably within the capability of a CLC409.
> 
> A friend recently brought me another commercial video DA, which I'm helping him modify for use as a 1/5/10 MHz DA.  It uses EL2099 video drivers, which are specified to provide 440 mA (typical -- 360 mA minimum) of output current.  This part should be able to drive 12 or more parallel back-terminated 50 ohm loads to +13 dBm, if desired.  (Like the CLC409, the EL2099 is obsolete/NLA.)
> 
> Best regards,
> 
> Charles
> 
> 
> 
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