Hi,
The following pic shows cmos current to voltage converter (for DC-DC converters application),can any one help me to know the design steps and suitable opamp required?
Your schematics appear complicated, perhaps more complicated than is required. They are labelled 'on chip'. Is your plan to fabricate an integrated circuit?
It is possible to do simple current sensing with a low-ohm resistor. A single op amp will be able to detect the voltage which develops on it.
This is part of your homework and education, not a product that exists or an ideal configuration. Just a basic current regulator which has intrinsic problems with load phase shift, so loop performance compensation is part of your design requirements.
Normally on-chip current sensing shunt is limited to 50mV max to reduce power, then using low offset high gain design to suit resolution specs which are unknown.
Many options need to be selected from your specs, which are unstated.