Actually, they aren't, and should not be confused with BJTs. The TIP120 is a linear integrated circuit with several components, including two BJTs.
And, since they are obsolete and almost completely irrelevant to modern design, will not be further discussed.
Other Darlingtons only consist of 2 BJT, so I distinguish between Darlington (principle) and TIPxxx (exemplar).
I am not understanding why you made this statement. Darlington devices are, by definition, a pair of bipolar junction transistors connected to function as a single bipolar junction transistor.
The TIP120 device has a pair of BJT’s and functions as a single BJT. Where is the confusion?
It does not, although the characteristics are vaguely similar to a BJT, as a 3 terminal device with current gain. Even a brief glance at the data sheet reveals large differences to BJTs, requiring different design approaches.
I really do not understand this insistence to stuff very different parts into generically named boxes.
@jremington, I have seen some of your posts in the Arduino forums and recognize you as one of the most helpful people on the forum. So, this discussion on the TIP120 seems out of character for you.
I am not understanding this.
TIP120-D.PDF (163.6 KB)
From the datasheet:
DARLINGTON 5 AMPERE COMPLEMENTARY SILICON POWER TRANSISTORS 60−80−100 VOLTS, 65 WATTS
Looking at the schematic for the device, there’s a Darlington pair with 2 resistors (8k Ω , 120 Ω) added. Again, I don’t understand your statement.
I definitely agree that setting aside the TIP120’s and getting proper MOSFET’s would be best.
It's a compound transistor.
Are you aware that a module like this:
may be cheaper than 4 darlingtons?
Besides, it contains protections you, with you level of knowledge about electronics, probably never even think of.
@jremington I think that I may have figured out the confusion. Regular bipolar junction transistors and Darlington Connection (pair) are not interchangeable devices.
Here is the Wiki definition of Darlington transistors:
Darlington configuration (commonly called as a Darlington pair) is a circuit consisting of two bipolar transistors with the emitter of one transistor connected to the base of the other, such that the current amplified by the first transistor is amplified further by the second one… It acts like and is often packaged as a single transistor.
In use, the Darlington devices function as a single bipolar transistor. However, their correct use is a single specific configuration of bipolar transistors suitable for them. Attempting to use them in other transistor circuits reveals that they are not standard BJT’s, but rather a pair of transistors.
So, it is completely correct to describe Darlington Pairs as bipolar junction transistors. However, their correct use requires understanding how they are different from other BJT types.
In this discussion, the original question occurred because the distinction was unknown.
My guess is that OP wanted a high voltage across the 330 Ohm resistor, which was intended to be replaced by the motor.
The chosen circuit, emitter follower, just doesn’t do that.
My guess is that OP wanted a high voltage across the 330 Ohm resistor, which was intended to be replaced by the motor.
correct!