Help with amplifier output!

If you want current gain and no phase inversion, with one stage of transistors, then you'll need "common collector" configuration.

For your PNP devices, hook the collectors to your minus supply. Tie the bases together. Each emitter will need a separate small resistor (to insure that the current shares equally), and tie the other end of all the resistors together. This will be your output.

The problem with this simple configuration is that you can only provide (sink) current from your minus supply. You have two options for being able to also source current from your positive supply -- add a (high power) resistor from the emitter resistors to the positive supply, or add another group of NPN devices, in a similar configuration as your PNPs, with their collectors to the positive supply.

The (high power) resistor approach will force you to run the amplifier in what's called "class A" operation. The latter approach can be run "class B" , "class AB", or "class A".

You should research the available literature describing high power amplifier configurations and design.

Bob

Hi Bob,

First, thank you for your reply. I forgot to tell you that i added another group of NPN devices. Now i will remake it following your idea. If having any problems, may you help me again?

Thanks, Lam

Hello Bob,

with your descriptions, I do not need to change 2 driver transistors. I only have to change groups of NPN or PNP. Now, for NPN group i can use a PNP to drive or not? Can you tell me this?

Thanks Lam