I want to study a simple class AB amplifier circuit using darlington power transistors. I thought that
perhaps the TIP110 / TIP115 or the TIP120 / TIP125 might be suitable. The reason that I want to use
darlingtons is because of the high input impedance that can be achieved thereby preventing
a previous voltage amplifier from being loaded down. I haven't done any more than think
about it and try to get spice models. I like to run a spice sim before I breadboard a circuit just to
see what I can expect in the real world.

Thanks,

RS

Hi Papabravo

The zipped folder is apparently too large to send.

RS

 

Hi Papabravo

The zipped folder is apparently too large to send.

RS

Here is a spice file in which I placed a TIP120.
Hope this will help.
RS

 

With no collector or emitter resistor to limit current, the Darlington in the post #23 circuit would try to destroy itself.

 

Simulators do not see if a circuit design overloads anything. This circuit shows it.

This class-A darlington circuit has an extremely high base current producing saturation with unlimited current from the power supply. Its load is a short piece of wire. It is definitely not a class-AB audio amplifier output circuit The darlington circuit is also not a class-A audio amplifier output circuit.

 

With no collector or emitter resistor to limit current, the Darlington in the post #23 circuit would try to destroy itself.

I know those resistors are missing. The point here is to see if the TIP120 is correctly set up. An approriate
circuit will come later.

RS

 

Why are you doing a simulation when the simulator does not tell you your simple circuit does not work?

The specs for a darlington or any transistor are a range of numbers from minimums for some of them to maximums for others of them. The simulator shows only darlingtons with typical specs. But you cannot buy one with only typical specs.
You need to design the circuit so that it works fine if the darlington has specs within minimum to maximum specs.

 

I know those resistors are missing. The point here is to see if the TIP120 is correctly set up. An approriate
circuit will come later.

RS

LOL