Voltage buffer

Most NPN transistors in my drawers will happily work at that voltage. I probably don't have anything with VCEO less than 20 or 30V.

The power to drive the output circuit has to come from somewhere else

-- I'm assuming you've got a DC power supply which is greater than the highest amplitude of your input signal.

If you do, why not just use an opamp as a voltage follower, like this (view in fixed font or M$ Notepad):

| | +24V | |\\| | >-------|+\\ | Vin | >---o----->

| 10-14V.---|-/ | Vout | | |/| | | | | | | | === | | | GND | | '----------' (created by AACircuit v1.28.6 beta 04/19/05

An LM741 will work just fine here. Or if your load requires more than

20mA, you can put your transistor in the feedback loop as a current booster, like this:

| | +24V +24V | |\\| | | >-------|+\\ |/ | Vin | >------| | 10-14V.---|-/ |>

| | |/| | | | | | | | === | | | GND | Vout | '---------------o-------o (created by AACircuit v1.28.6 beta 04/19/05

Either way, your output voltage will track the input within a few millivolts, and your signal source will be unloaded. Much better solution than a single transistor.

Good luck Chris

Even the common-as-beans PN2222A has a Vceo max of 40 volts, according to the first datasheet I found. Power dissipation should be under

100 mW, well under the 625 mW that the 2222 claims to be happy with. So yeah, I think a random junk-drawer transistor has a good chance of working in this circuit (since all the transistors in my junk drawer seem to be 2222s or BC547s).

--
   Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1

I'm assuming there is a reason you cant use a voltage divider if the transistor is not rated high enough?? B

Okay, this was a basic misunderstanding on my part. I assumed that the maximum Vbe rating is what I am allowed to apply to the transistor base. For the above scenario a regular 2N2222 turned out to work just fine.