Voltage follower in transistor form (common collector) - some questions....

Hi,

To date, whenever I've needed a voltage follower, I've simply pressed an unused opamp into service (typically I use quads & seldom are all the opamps in use), but now I need to buffer a voltage ...but I'd like to use a tranny.

I believe the config I need is a common collector, to some questions...

1. Do they exist where the emitter resistor is integrated into the transistor package? (to save component count)

2. Is there any voltage loss between the base voltage and emitter voltage - for example, if I place 1.8V DC on the base, will I get 1.8V on the emitter? If not, how much will the voltage deviate?

3. I actually need the resulting ouput voltage to be quite low impedance - how do I know what the output impedance is wrt a common collector arrangement? (is it as simple as saying it'll be whatever value the emitter resistor is?)

4.Is there any better tack I can take which give a low parts count, low pin count, low impedance, low power, voltage follower? (an opamp seems overkill for my needs)

Many thanks.

1. no
2. From B to E there will be 'one diode' of loss or drop. 0.6 volts.
3. Yes emitter resistance may apply. The transistor is a current amplifier so...If the circuit on the base can deliver 1mA and the transistor has a HFE of 100 then the emitter can deliver 100mA. Note Hfe depends on current, frequency, temperature, etc.
4 An emitter follower (using one transistor) can only pull in one direction. There is probably a resistor to pull in the other direction.

Thanks for your input - hmm, not sure it's going to be suitable for my needs then - I can feel a low cost regulator at the required voltage coming one!