21 Dec
2007
21 Dec
'07
8:55 a.m.
From: dkelvey at hotmail.com
To: cctalk at classiccmp.org
Date: Fri, 21 Dec 2007 08:21:53 -0800
Subject: RE: The 2N2/256-BSCP [was: Homebrew Drum Computer]
Hi
Another negative resistance device is the DIAC. These are
really cheap but these are knee type curves instead of
S type, like the TD and Lambda.
One would have to rearrange these in a parallel configuration
for a latch or flop, similar to the neon circuits.
The TD has the advantage that the stable state is lower
current, not higher current.
The disadvantage is that that tends to increate the impedance
of the storage net making it less stable and more susceptible
to noise. That is why I recommend the shunt resistor to
decrease the impedance.
Dwight
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From: mcguire at neurotica.com
Date: Fri, 21 Dec 2007 08:52:06 -0500
To: cctech at classiccmp.org
CC:
Subject: Re: The 2N2/256-BSCP [was: Homebrew Drum Computer]
On Dec 21, 2007, at 2:07 AM, dwight elvey wrote:
Hi
To better approximate a tunnel diode, you'd have
to put a resistor in parallel. I don't recommend doing
this as it only degrades the negative resistance.
Still, if one was to use a pair of these for a flop, it
might be more stable since at the higher voltages,
unlike a real TD, it completely shuts off. Without the
shunt resistors to bypass some current the circuit
might oscillate.
Dwight
As a cheaper alternative to a tunnel diode, do a
search for
a Lambda Diode. I used one of these circuits once to make an
oscillator that ran at over 100MHz.
Oh my, there IS an almost-equivalent-to-a-tunnel-diode circuit!
That looks really, really neat...I will have to play with that!