T&L Publications

No, the old thread here where jollyrgr posted that circuit was orginally started by me in 2006.

I believe that ckt was used in a commercial product. In fact I knew someone who was using a minor variation of it back in 1997 to run low power fluorescent lamps. I think he replaced the inductor with a transformer and ran the circuit from 12V. That guy was a talented power supply designer.

Hey John

What tool did you use to do your simulation?

I tried to create the same simulation in PSpice with different results... probably something I did.

Great Job!

Sambuchi wrote:Hey John

Who is John? Jwax?

oops sorry peter... I was just catching up the entire thread and forgot who did the simulation.

When I make it in PSpice Transient simulation with the same parts...
"VSRC source with a TRAN=1.5 then setting up the print step and final time"

Your second simulation you have VLoad at 2.8V my simulation shows 1.8V

Sambuchi wrote:oops sorry peter... I was just catching up the entire thread and forgot who did the simulation.

When I make it in PSpice Transient simulation with the same parts...
"VSRC source with a TRAN=1.5 then setting up the print step and final time"

Your second simulation you have VLoad at 2.8V my simulation shows 1.8V

I used Linear Tech LTSpice.
Here are the files

Hello everyone. The circuit mentioned in this thread really sparked my interest. So much that I am running simulations with two tools and spent most of yesterday playing with different components in the circuit.

I understand this topic was discussed in a previous thread but maybe someone here could shed a little light on this circuit.

I understand how this circuit works to and extent. Were I an failing to grasp is the transistor selection. I am comparing the ztx849 and the 2n2222. Now I see that the ztx849 is a high current transistor and the Ic [collector] can go up to 5A ... and the 2n2222 is a general purpose transistor Ic 1A

I am wondering when using the 2n2222 for Q1 you can not get the same results. I notice that the Ic for a 2n2222 is not getting close to 1A... so I am not sure if thats the limiting factor for the 2n2222. Well, I was just curious to know.

Thanks again.

Sambuchi wrote: I understand how this circuit works to and extent. Were I an failing to grasp is the transistor selection. I am comparing the ztx849 and the 2n2222. Now I see that the ztx849 is a high current transistor and the Ic [collector] can go up to 5A ... and the 2n2222 is a general purpose transistor Ic 1A

I am wondering when using the 2n2222 for Q1 you can not get the same results. I notice that the Ic for a 2n2222 is not getting close to 1A... so I am not sure if thats the limiting factor for the 2n2222. Well, I was just curious to know.

The original circuit is a simple one transistor inverting amplifier,
and somewhat dependent upon the actual transistor type. For
a low noise pre-amp a high gain, low noise, small signal, device
would be a good selection. However, most of us have our
favourites from the huge array of general purpose types.

These include the 2N3904, 2N3906, 2N4401, 2N4403 for
which we have good SPICE models.

For higher power operation the 2N2222 and 2N2907A are
popular, and would work in this application but may show
lower performance, especially for noise.

None of these devices are being pushed anywhere near their
limits for current, voltage, or power dissipation.

The ZTX849 (FTX849) is a secret weapon! It was introduced
specifically for low voltage (single battery cell) high current,
high gain, high speed, saturated switching, in DC-DC converters.
I use it in building or repairing anything like a CCFL inverter, LED
Solar lantern inverter, or Royer circuit. There are good LTspice
models for it. It's worth the premium price and it even beats
some MOSFets for low voltage applications.

There are bipolar transistors specifically intended for
low noise operation (first stage in a high gain chain).
The Fairchild PN2484 is one example.

Hi again,


Yes, Jwax is John.

There are also the 2 transistor collections by Roman Black.


http://www.romanblack.com/smps/smps.htm


Colin