Re: Q - Driving HV DC pulses? (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 7 Oct 2005 16:47:38 +1300
From: Malcolm Watts <m.j.watts@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Q - Driving HV DC pulses? (fwd)

On 6 Oct 2005, at 19:34, High Voltage list wrote:

> Original poster: <sroys@xxxxxxxxxxxxxxxxx>
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Wed, 05 Oct 2005 18:49:20 -0400
> From: Jeff Bullock <jeff@xxxxxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: Q - Driving HV DC pulses? (fwd)
> 
> Hi Matt ,
> 
> Thanks for your reply.
> 
> > ---------- Forwarded message ----------
> > Date: Tue, 4 Oct 2005 12:20:14 EDT
> > From: Mddeming@xxxxxxx
> > To: hvlist@xxxxxxxxxx
> > Subject: Re: Q - Driving HV DC pulses? (fwd)
> 
> > Hi Jeff,
> >
> >     Yes, tubes can be and have been used as switches.  All of the
> >     earliest
> > digital computers and radar systems were vacuum tube  devices. The
> > first multivibrators were VT devices. Power handling  capabilities
> > of a single
> tube range
> > from 1 mW to 50 KW. Plate voltages up to 10  KV are not uncommon for
> > transmitter types.  For your application, you will  need one with a
> > small
> "knee" and
> > steep slope.
> >     I would recommend that you get a copy of RCA manual  TT-5
> >     (reprints
> from
> > Antique Radio Supply, Tempe AZ) and a book on digital  circuits
> > published 1942-1962. Perfect square waves do not exist in the real
> > world. You can, however, get to the point where the rise and fall
> > times are such a tiny fraction of the pulse  width that it looks
> > square and works for most purposes.
> 
> Good info. Using tubes are not by any means a the best choice for this
> application. Solid-state solutions are ideal. Tubes may, however,
> become necessary to switch the high voltages quickly. BTW, it seems
> like the triac is a close solid-state relative to the triode.

It isn't even close. For one thing, a triode doesn't latch on. For 
another, saturation/conduction voltages are totally different. A 
MOSFET might be considered a close relative of a triode but even 
there the dynamic input capacitances and saturation voltage are quite 
different.

Malcolm