Re: Common collector load driver

On May 5, 12:57 pm, rich <rsoennich...@xxxxxxxxx> wrote:
Hello all,
I need to to drive a 300mA resistive load with an variable voltage
of 0-30V. Right now I have a NPN transistor in the common collector
configuration.

The collector is tied to the supply voltage which can be 10-30V. The
base is driven from 0V up to the supply voltage.

This works just fine up to a supply voltage of about 20V. I can vary
the base voltage from zero to that and get a nice output without too
much heat.
Above this however I get way to much heat, even at small loads.

The transistor is in a sot-223 package with a pcb copper pour area as
a heatsink.

What is a better way to construct a voltage follower that will
dissipate less heat? Perhaps switching to a p-channel mosfet?

Thanks

Rich

Rich,

Max power will be about 9 watts at 30 volts. What is the number of
the transistor you are using and the config. one side of the resistive
load is connected to the collector and the other side to the 30 volt
supply, the emitter is grounded or tie to the 30 volt power supply
return. The control voltage is connected to the base thru a base
resistor. Is this your config?

Den
.

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