who knows this transistor?

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Hi all,


I have here a transistor where I know nothing about. The only thing I know that it is a PNP transistor.
Here's what's written on it:
SK
A957
170

I searched the web about this transistor but couldn't find anything. I hope maybe someone could give me more information about this transistor cause I would like to simulate the schematic where it's in in LTSPice....


Thank You!

dolf
 
Since I couldn't get my hand on a spice model for the 2SA957, I looked for a model of the MJE15031 which according to what I've found could also do the job.

Hope it won't make a big difference.

Thank you very much for all the replies though!

@Netlist: I'm doing my thesis there and this simulation was part of my work to achieve my goal.
 
Thanks!

Actually it has nothing to do with audio except for the fact I use the Quad 405 schematic. My goal is to make an amplifier which can deliver up to 10A. Hmmm, maybe it's easier to copy paste my abstract to give you an idea:

AMPLIFIER FOR THE RESEARCH OF MAGNETIC MATERIALS
The magnetic materials in this research are those who are used in transformers of switching power supplies. For this research a voltage is placed at the coil around the core of the transformer. The frequency of this voltage can be as high as 100kHz. Meaning the amplifier has to have a bandwith of 100kHz, after this frequency the amplification may decrease with 20dB/dec untill 2Mhz is reached. The coils which the amplifier should be able to handle have a value between 10µH and 1000µH. The amplifier demands an adapted design because the amplifier should be able to deliver currents as high as 10A, and should be able to handle very low impedances at it’s output. For this research there is the necessity of an adjustable DC-offset at the output of the amplifier. To achieve our goal we started from an existing amplifier design of QUAD which will be adapted to the needs of this research. The most important adaptions will be the bandwith of the amplifier, a stable output when the load is very inductive and the possibility to adjust a DC-offset at the output.

I have studied the feedforward and current dumping principle of the Quad but thought I might better simulate first how it acts under these conditions. I'm still working on it, it's the first time I'm working with LTSpice...

The 2SA957 were transistors for T7 and T8 which I got from my promotor (schematic: http://quad405.com/405-1schematic.pdf)

greetz
dolf
 
Hi D.O.LF

Just a thought-
if you are going to use reactive loads, then I would advise using a simple "blameless" type amp. based on a "non-overloadable" design with single Miller stabilisation.

The beauty of this is that it is unconditionally stable, and won't object to inductive/reactive loads.

The downside is that if the load and frequency are not optimised, the power transistors have to dissipate the 90-degree out-of phase current = worst case for dissipation.

An outline of the concept would be to build a power stage with a few MJ21193/21194's and MJE15031/2 drivers (or similar 2SA types). To reach 10A routinely, you will need at least two MJ's in the output, but for low impedance loads (you don't say how much power is needed) I'd guess four parallel devices would fit the bill.

Depending on how hard you intend to drive the amp, you may want to use a driver for each pair of outputs (i.e. two drivers/four output per stage, but maybe this is "armour-plating")

You can easily make sure that the input stages won't overload using correctly valued emitter resistors.

I've mentioned this in other threads, but with 6 mA input current source and 330 ohms, 1V inputs won't cut off the input stage at any frequency.

You can design this for 10 MHz unity gain, and it'll be pretty robust.

cheers
John
 
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