Re: Collector resistance of power bjts


"Eeyore" <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in message
news:4579FDA5.C7735D53@xxxxxxxxxxxxxx
| I just happened to be curious about a typical value for the collector
resistance
| of a power bjt ( such as in an audio amp ) and to my surprise the data that
I
| had handy didn't have any curves for the output characteristic ( Motorola
| Bipolar power data rev 6 - and I can't locate the other 2 data books I was
| looking for ).
|
| Before I go trawling various web sites randomly, has anyone got any quick
| suggestions for where to look first ?
|
| Graham
|

Try looking at the Spice Models. The Early Voltage divided by the collector
current is the "collector resistance" (Ro ~ VAF / Ic). There is a
considerable spread in the Early Voltage and it usually has to be determined
empirically. In addition NPNs usually have a higher Early Voltage than the
complimentary PNP but not always.

At 1 amp the collector resistance can be expected to be in the order of a few
ohms for some types to over several hundred ohms for others.

Dan Thomas

.