Does this comparator consist of BJTs?: https://www.fairchildsemi.com/datasheets/LM/LM2903.pdf

From its schematic diagram they are drawn like that. But I am not sure if it is the case always.

I mean I couldn't find any written hint besides the way transistors drawn. Sometimes the data sheets mentions such as: "BiFET Op Amp". I guess this means the opAmp is using BiFET transistors? But sometimes there is no written info.

Can we rely on the way transistors drawn in a data-sheet?

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    \$\begingroup\$ What is the motivation to understand the internal circuitry? \$\endgroup\$ – Umar Mar 4 '16 at 9:45
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    \$\begingroup\$ It's hard to verify without all the die layers. The schematic shown in the datasheet is often a simplified "equivalent circuit" that may omit technical details like transistor geometry or ESD protection structures. \$\endgroup\$ – MarkU Mar 4 '16 at 10:19
  • \$\begingroup\$ "Can we rely on the way transistors drawn in a data-sheet?" - this seems such a broad question, I'm not sure if you're expecting aynone to give you a simple yes/no answer or an essay on the variable and transient quality of datasheets in general. Can you make the question a bit more specific to your problem? \$\endgroup\$ – Roger Rowland Mar 4 '16 at 10:19
  • \$\begingroup\$ There is no such thing as a BIFET transistor. A BIFET opamp uses both Bipolar and FET transistors to get the best of each. Where a sufficiently detailed schematic is shown, I would rely on it. (Hmm should have read @FM's answer before commenting!) \$\endgroup\$ – Brian Drummond Mar 4 '16 at 12:41

Does this comparator consist of BJTs

If you look at the schematic present in the datasheet:

enter image description here

Then YES looks like all bipolar to me. But there are some diodes ?

These are either also BJTs used as a diode (connect Base to Collector) D5 and D6 will be such devices.

The diodes at the input can be "real" diodes made from the layers which are also needed to make the other transistors. Remember that a BJT consists of 2 PN junctions in antiseries !

BiFET transistors

There is no such thing as a BiFet transistor! What they mean is that the device (opamp) is made using a process in which they can make BJTs but also J-FETs (Junction FETs). Or Bipolar devices and FETs, marketing name: BiFET. A usual application for this is to use the JFETs at the input so that the input impedance becomes very high. Most of the other components in the opamp will be BJTs as these provide more gain and can be used for current mirrors etc.

Can we rely on the way transistors drawn in a data-sheet?

A manufacturer would never lie in a datasheet, what can be is that they hide some of the real circuit for reasons of protecting their design or just showing a simlification of the design.

But in the end to you as the user of an IC, it does not matter what is inside the device. All parameters that matter to you should be listed in the datasheet, how the manufacturer achieves this is their own business. That's why you seldom see a full schematic in the datasheet.


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