SSTC output stage questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>


For driving solid-state "magnifier" tesla coil I am currently using the 
complementary bipolar bridge output stage below to drive an air-cored HV 
transformer at near 750kHz.



+30V---------+

|

o /

T1 sec(a) +----+-----| NPN

| | \e

3t | |

| | |

+----|--Cb--+--Ce--+

| (a) | (a) |

| | |

| /e | |

T1 primary +-----| PNP | L3

o \ | T2 |

----+ | | +----+

| 0V----------+ | |

12t 18t 480t

| +30V --------+ | |

----+ | | +----+

/ | |

T1 sec(b) +----+-----| NPN | GND

| | \e |

3t | | |

| | | |

+----|--Cb--+--Ce--+

o | (b) | (b)

| |

| /e

+-----| PNP

\

|

0V-----------+

The power transistors in the bridge arms are connected as emitter-followers;

their bases are driven by antiphase signals from the pulse transformer T1

(wound on ferrite toroidal core).

The base capacitors Cb(a) and Cb(b)serve to limit the base drive currents 
in the respective arms.

The power transistors are TIP41 and TIP42 respectively.

THe primary drive signal for T1 comes from a from a TIP41 npn power 
transistor connected as a common-emitter amplifier

the base of which is driven by Pin 3 of an equal mark/space 555 astable, 
via a capacitor-diode network (not shown).

Performance is limited by low-power of the circuit. Current draw from 30VDC 
is circa 2 Amps and all the power transistors need heatsinking. I can draw 
corona from the extra coil (100m hookup wire wound around a plastic 
bucket)by bringing a grounded wire really close to it and draw short but 
hot arcs from the bare end (there is no topload as yet) by touching the 
wire to it and then withdrawing it a short distance.

The electric field around the top of the extra is INTENSE- it ights 
fluorescent tubes, neon bulbs and the gas in a Crooke s radiometer 
positioned a short distance away.

I would like to improve performance.

Is it OK to use complementary-emitter bipolar bridge to drive the primary 
of a Tesla coil -magnifier or otherwise or would a non-complementary output 
stage be better?

Is it OK to use the pulse transformer in this way?

With regard to the single ended common emitter amp that drives T1 primary, 
would a complementary emitter-follower stage do the job better?

Are there any suggestions as to better transistors than TIPs 41/42 for use 
in this application?