How to Start Designing a Two-Stage Differential Op-Amp with 6 Transistors?

It is required to design a two stage differential-input single-output opamp with certain specifications ( min. voltage gain bandwidth and max. dissipated power and DC rails).

I am allowed to use only up to 6 transistors with certain types of transistors allowed. All I need to know is from where should i begin??. I would be grateful if you attached any helpful sites or references as well. Thanks

The best reference for cmos op amp designing is razavi's " cmos integrated circuit design" book .it will give you the best insights in cmos circuit designing. and then gray's " analog circuit design " is good. but first you consider the razavi's one specially chapter 9 and 10 that are related to op amp design.

Hi noha,

Here are notes i found. Hope it Helps

Opamp Design
Analog Integrated Circuit Design
Basic OpAmp Design and Compensation

The classic book on op-amp design is "Operational Amplifiers: Design and Applications" by Tobey, Graeme and Huelsman, from 'way back in 1971. Bipolar transistor design, very basic, but complete. Don't know if it's available online, but you can usually find a used copy pretty reasonably. We used to make discrete 4-transistor video op-amps for our designs at RCA in the '70s when integrated ones were still expensive.

Ok, you need a 2 stage diff-input, single output opamp.

When faced with a problem like this, ignore the specs for the meantime and
focus on the architecture of your circuit.

An op-amp is essentially a differential amplifier input with cascaded amplifiers.

A differential-input, so 2 transistors back to back with its emitter/source common, base 1 and base 2 serving as the 2 inputs, and 2 outputs drawn from their collectors respectively.

This leaves you with 4 transistors. You can use them as voltage gain amplifiers/current gain amplifiers/both whatever gain is needed at the output (voltage dividers are the most stable if you are after power gain).

For the DC rails, that would depend on the bias voltage. So if you were given, say, 10V DC rail spec, then bias the amplifiers with 10V.

Definitely look at various resources. However your specs almost define what you must do.
You said two stages and 6 transistors. A simple google images search yields this design that my fit your specs.

"6 transistor amplifier()":https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcRdlZmwSOsdSpVWIQnV-Rzc1qNg-VKtOYfnR_hvwOHkz1XX6V_k