On a breadboard I built the circuit up in the following manner:

I used two resistors in parallel(98.9 ohm and 98.2 ohm = 42.7 ohm) to achieve a Ic of 92.3mA. (The current I want in the collector.)

The Beta (Hfe) for the bu337-25 is 160.

I calculated my Ib using the formula: Ib=Ic/hfe which came out to .0005768A

I then calculated my Rb using the formula: Rb=4.97-.7/.0005768 which gave me 7402.9 ohms for Rb.

The closest I could come to the Rb value was 7170 ohms.

This value made my current in the Vb .0005857A which should sat. the npn more. This changes my beta to .0923/.0005857 = 157.58.

After I built this circuit and probed it w/ my meter I found the following values:

Vb: 4.2v, Vbe .733v (it is above the threshold), and Vbc of .607v.

Vce was .125v.

All of which met my requirements of Vb being larger than Vc and Ve.

I made some alterations to the circuit and changed my Rb to 10,475 ohms which gave me a Ib of .000397A(actual meter reading) calculated to .0004009A. I was looking to get my Vce up to the .2v that I had read it had to be. I achieved a value of .206v for Vce. These also met all my requirements. But the beta was 232.49.

I understand that you want to add 5-10% to your Ib to really get the npn into saturation.

In the data sheet I am confused when they give you the beta of 160 as a min and let's say 400 as a max. This I do not understand because I have calculated values out that gave me a Vce of .120 and the beta was around 157.58 which is under 160 on the datasheet so is this still in saturation? DO I try to get the npn into saturation with 106 beta or 400 beta or somewhere in between?

How much Vce should I try for? Is .120 enough?

The graph for the Vce vs Ic doesn't seem to give me the correct numbers vs. what I see on the breadboard.

What is the best way to look at this in terms of saturating the transistor to use it as a switch?

Thanks for your time and help.

-Val