Replacement for TIP125 Darlington

[Adriaan]

Hi,

I am trying to build an H-bridge. I got a diagram with two TIP125
Darlington transistors and two TIP120's.

I cannot get my hands on either of these components. What can I
replace them with?

Thanks,
Adriaan

 

[CWatters]

"Adriaan" <adriaan18@webmail.co.za> wrote in message
news:fe15f961.0407250855.26893ce9@posting.google.com...

Hi,

I am trying to build an H-bridge. I got a diagram with two TIP125
Darlington transistors and two TIP120's.

I cannot get my hands on either of these components. What can I
replace them with?

Farnell-in-one (a big distributor in the UK) has them but I don't know if
they export and there might be a minimum order value?

http://uk.farnell.com/

...try also cross ref database...

http://www.ee.washington.edu/circuit_archive/parts/cross.html

This says the TIP125=TIP126=TIP127
which may not be helpful unless you look up the TIP127....

TIP127 =
2N6035 2SB673 TIP127
2N6040 2N6041 2N6042
2SB791 ECG262 2SB791
ECG262 2SB791 ECG262

Suggest you repeat this for the TIP120

 

[Watson A.Name - \"Watt Su]

"Adriaan" <adriaan18@webmail.co.za> wrote in message
news:fe15f961.0407250855.26893ce9@posting.google.com...

Hi,

I am trying to build an H-bridge. I got a diagram with two TIP125
Darlington transistors and two TIP120's.

I cannot get my hands on either of these components. What can I
replace them with?

Thanks,
Adriaan

Because you're using these for a switch, a darlington is not the best
choice. Darlingtons have a minimum V drop of a volt or so, which causes
a lot of power to be wasted in the power transistors. You should use
two separate transistors, with the collector of the first or driver
tranaistor connectred to the supply, not to the collector of the second
or output transistor. You then use a current limiting resistor from the
emitter of the driver to the base of the output transistor.

Another alternative is to use power MOSFETs which have very low on
resistance. This allows a very high current with a minimum of
heatsinking.