Hi, Can anyone say how the below circuit works?! It includes two digital transistors that are packaged together into an IC!

 

Hi, Can anyone say how the below circuit works?! It includes two digital transistors that are packaged together into an IC!

An inverter. A high in makes the output low. You can see it work if there is a pull up resistor on the output.

 

It is a complementary pair that enables the designer to work with DC coupled data without a diode drop offset.

 

The function is that of a switch. It forms a digital pattern of on switches and off switches.

 

You could also see it as a level shifter if you take the output from the right collector and provide a higher supply voltage where the original drawing shows the output.

I would like to disagree that those are, "digital" transistors. They are just transistors, which you can use for digital or analog purposes.

 

The whole point of the digital transistor is to reduce the parts count and make the electronic gizmo smaller.

 

I would like to disagree that those are, "digital" transistors. They are just transistors, which you can use for digital or analog purposes.

Not exactly, we have different design rules for digital or analog transistors. Thicker gate oxide/junctions, drive capability, etc ... or things like GM/high gain for analog transistors. There might be no difference of spice model but the physical construction can be noticeably different for things like ESD resistance.

 

The whole point of the digital transistor is to reduce the parts count and make the electronic gizmo smaller.

Good profit on space saving when the chip includes 4 resistors!

we have different design rules for digital or analog transistors.

Your description would be more clear if you stuck with bipolar transistors as per post #1. GM/high gain is always good to have, digital or analog, but are some of these bipolar chips optimized for less of some other property if they are just for analog or just for digital?

I can easily imagine these designed for 5 volts for digital only because lower voltage limits are associated with higher current gain. I guess higher frequency operation is preferred for digital only because modern CPUs go upwards of a GHz but analog people don't even play with GHz unless they specify RF transistors from the get-go.

 

Your description would be more clear if you stuck with bipolar transistors as per post #1. GM/high gain is always good to have, digital or analog, but are some of these bipolar chips optimized for less of some other property if they are just for analog or just for digital?

Sure, there are optimizations (while everything else remains the same) for general bipolar transistors vs analog. For digital gate or base capacitance is minimized for maximum turn on and off delays, maximum speed and minimum power dissipation influence physical design, doping and a thousand other things. For analog you have things that optimize via doping, structure orientation, etc.. for possible higher slew rate, lower distortion and leakage in the active region vs cutoff and saturation.
.

 

I will use it as a buffer.

 

Well I'll use it as a sine wave to "somewhat" of a square wave converter