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designing an internal circuit of an Op Amp

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Junior Member level 3
May 3, 2015
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I wanna design an internal cuircut of an op_amp with some futures like with specified gain and internal current and power and working with a special power supply which given

i khow how should be input stage or ... To reach that gain for example

But i dont khow how to start ?
I mean from which point ?
how to assign the numbers for the biasing points for example

prior thanks to any one who show me the way !

An opamp has extremely high gain at DC and low frequencies of 50 thousand to a few million. Because the transistor circuit causes phase shift and delays at high frequencies then a compensation capacitor is used to roll off the gain at high frequencies so that negative feedback does not cause oscillation. The gain begins to roll off at about 10Hz.

Since the circuit for an opamp can be inverting or non-inverting then a differential input is used. The output should be push-pull and not have crossover distortion so a complementary pair of emitter-followers is used at the output.
You must decide if your opamp must have low supply current but then its output current will also be low and its high frequency response will be poor.

The datasheet of an opamp usually shows its schematic. Did you look at a few hundred of them?

ok but my big problem is how to bias that
i use the telescopic cascode for the differential stage in order to higher the gain
so i have to set 3 biasing , but dont khow how ?
if any opamp shematic will help me as you mentiond would you recommend some?

The differential input of an opamp does not have high gain. Instead, the following transistor stage has high gain.
It is simple to correctly bias amplifier transistors.

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