Electronics Forum / Basics / February 2007

I'm analyzing a ciruit which contains TIP31 NPN transistor.
The hFE (current gain) on the datasheet is 25 (Vce = 4V, Ic = 1A),
10 to 50 (Vce = 4V, Ic = 3A).
The circuit is about a battery charger and it handles various voltage,

I am looking at safety issues concerning transformers.
Basic question, I know, but other than an open circuit due to a
winding burnout, or maybe a shorted turn, how else can a transformer
fail?

I am trying out a self made high voltage ferrite transformer for
insect killer (mosquito),according to the mannal, the output of the
secondary high voltage winding should be on the outer of the ferrite
core, i like to know is there any difference if i put the high voltage

test

I need to replace some optocouple ( round shape plastic casing ). The
optocouple which trigger a triac and control by a TTL IC, there are
printing on the optocouple "MOD 725", i had desolder some good
optocouple and measure both side with two output lead, the DMM show

No, I'm not looking to set off bombs, but I was wondering if I could
redesign this ridiculous thing:
http://home.att.net/~Tom.Horsley/markII/markII.html
right now, I watch for the display lighting up so I can get notified

I would like to know why some DACs have current output instead of
voltage output. Is there any advantage with one or the other. Thanks.
Amish

Can anyone tell me a good book or reference that helps me out in
marchand balun design. Where all it is used and what for ?
Also the basics of various transitions in microstrip and the need for
it, please.

First, thanks to everyone who responded to my earlier question about
combining the secondaries on my toroidal transformer.  That was the
thread from here:  http://snipurl.com/1amow
I like the voltmeter test idea...I will try that method...thanks!

Hello, I have a question about driving an LED with a 7406.  Basically
I have an MCU going into a 7406 inverter going into an LED going to a
resistor R and that going to a 5 V power supply.  All in series, and
I'm trying to find the value for R that would make this thing work....

I am a std of BE electronic engineering. Now a sophomore, I had a bad
result in the freshman year. An overall result of 64.6 percent and
failure condoned in two subjects namely basic electrical engineering
and chemistry.

I tried to sharpen and re-tin a tired tip once and failed. I'm about
ready for another new one and was wondering again if it's possible and
what the proper technique is after grinding a nice new point?
Thanks,

Hi, I'm hoping someone could help me create a very basic circuit which
would:
Count the number of pulses it receives per second (from a 555 timer,
or a switch, for example) and if the number of pulses per second is

Can anyone give me some directions on how to develop a circuit
simulator from scratch. I need to develop a simple spice compatible
simulator,that can read in spice netlists. I will be using C++ to code
the simulator. I need to support only simple R,L,C, diode and mosfet

Any ideas on the best way to mute/blank the output of a 400 watts RF
solid-state amplifier (< 50 mhz) for pulsed (microsecond) operation?