From: G0MRF@aol.com
Message-ID: <fe.7b06691.2858890a@aol.com>
Date: Wed, 13 Jun 2001 05:14:50 EDT
Subject: Re: LF: RE: 73kHz tests tonight
To: rsgb_lf_group@blacksheep.org
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

In a message dated 6/13/01 8:49:55 AM GMT Daylight Time, ACTALBOT@dera.gov.uk 
writes:

<< One option would be to use the TC4428 driver chip.  This has one inverting
 and one non inverting driver.   Drive both inputs in parallel and connect
 the FET driver transformer primary, now with twice as many turns, between
 both outputs.  That way you can double the drive capability without running
 into the problems with the unequal switching times that can give trouble
 when trying to parallel up two devices with totem pole outputs
 
 Andy  G4JNT
  >>

Just a thought....

The 4428 has different propagation delay times in each section due to its 
'non-symetrical design. Although this may be minor I could see the difference 
on a fast scope and it did affect the switching in a 1500kHz transmitter I 
was working on.
It may not be important at 73k, but it's worth remembering.
I recall using 2 TC4429 chips which I seem to remember are single high 
current inverters.

73

David 'MRF