The output stage in your attachment is not CB-CE, nor is it similar to the output stage in the MC1435 datasheet.oh ok..
consider this mc1435 ckt. it has cb ce config at its output stage, so it has to have high output impd rite??
this ckt is given as the general circuit for all opamps in the text books..
The output stage in the MC1435 datasheet is not an emitter follower. It is a Sziklai pair (compound transistor), and the output is from the collector, which explains the 1.7k output impedance spec.I would say that must be a 'simplified' representation of the actual chip design.
The MC1435 Data sheet also shows that same emitter follower output stage with a 2K resistor from output to negative supply, but the data characteristics do not fit that configuration.
Datasheet here: http://www.datasheetarchive.com/pdf-datasheets/Datasheets-110/DSAP0010025.pdf
Example: With a +/- 6V supply, the short-circuit output current is given at typically 17mA.
Although the emitter follower stage could source significant current, the 2K resistor in the schematic would only sink 6mA with the output shorted to V+ (with a total 12V between V+ & V-).
The opamp must actually have an active output circuit to allow it to sink that much current.
However, the data also says it can only guarantee +/- 2.5V into a 10K load..
I think it is a rather poor example for educational purposes.
(The datasheet specifies the output impedance is 1.7K)
hi, for an opamp internal circuit, we connerct a ce-cb config in the output stage rite,
a ce cb config has high output impedence. but an opamp has a very low output impedence.
can anyone explain me y this s so or have i understood wrong.
Look closely. They are not the same.I was not clear on the 'CB-CE' bit, but opamp schematic is the same as one section of the MC1425 as per the datasheet.
(Note the datasheet shows both sections, the lower drawn inverted).
I don't see the inverted output between the two designs. See the annotated attachment.Yep, there are a few details different, I was only looking specifically at the output transistor & load resistor.
The changes *could* be transcription errors? The mid section is missing a load resistor, without which it could not work.
There again, the links from the input stage to the mid stage are reversed, which would account for the inverted output between the two designs.
Only because the OP brought it up.Why are you looking at the antique MC1435 opamp? It has nothing that is common with a modern opamp and is no longer available:
Its max supply voltage is very low.
Its max gain is very low.
Its input impedance is low.
Its frequency response is very poor.
Its supply current is high.
It needs external compensation capacitors.
Its output is class-A instead of class-AB.
I think the word you want is "complementary". It is not "ce cb". There are no common base transistors of either of the output stages that we looked at.now i am even more confused..
can i have a detailed conceptual analysis of the outout impedence..
including tat ce cb confirmatory part pls....
He's probably been out of industry so long (maybe never), that that's all he knows. If this is the case, it's not good.The school teacher should be fired for having students analyse such an old garbage opamp.
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