In BJT transistor is saturation current and peak current are same? if not then what's the difference between them. I'm trying to find the Ic max for 2N2222 transistor.

 

The ICmax can be found in the datasheet absolute maximum ratings section.

This is the maximum collector current which the transistor can handle continuously.

The collector saturation voltage is given in the electrical characteristics section of the datasheet.

Note that there are two saturation voltages for different collector and base currents.
You can think of this voltage as the minimum voltage the collector can reach at the specified collector current. The collector current is not being controlled by the transistor but by the collector load.

Therefore the saturation current can be, for instance, 1mA if the collector is connected by a 5k resistor to a 5V supply. That absolute maximum collector current still applies though.

 

In BJT transistor is saturation current and peak current are same? if not then what's the difference between them. I'm trying to find the Ic max for 2N2222 transistor.

Is this still homework?
https://forum.allaboutcircuits.com/threads/base-current-calculation-for-2n2222-transistor.147544/

 

Saturation is a voltage, "peak" is a current. Beyond the abs max peak current the transistor may probably suffer a catastrophic thermal failure. Saturation voltage is telling the voltage across the transistor when it can't turn on any more. The current can still be increased but the voltage will not change much.

 

The ICmax can be found in the datasheet absolute maximum ratings section.
View attachment 150114
This is the maximum collector current which the transistor can handle continuously.

And further note that this is the maximum current that the device is rated for when it is strictly the current that is limiting things. If heat, for instance, is limiting things, a lower maximum continuous current will be dictated by those considerations.

For instance, the Fairchild PN2222

https://www.fairchildsemi.com/datasheets/PN/PN2222.pdf

Has a maximum collector current of 600 mA.

However, it also has a maximum collector power dissipation of 625 mW at an ambient temperature of 25°C and a maximum collector-emitter voltage of 30 V. Under those conditions, the heat considerations limit the collector current to less than 21 mA. In order to reach the full continuous current of 600 mA, the Vce can be no more than right about 1 V, so not TOO far above saturation -- in fact, 1 V is the Vcesat value at 500 mA, so that's just about right.

All else being equal, the collector current in saturation will be higher than the collector current in the active region simply because the Vce is the smallest when in saturation, hence lower power dissipation.

Also note that this current limit is for CONTINUOUS operation at that level, which generally means that it IS the thermal considerations that are at play. You can get by with quite a bit higher peak currents if the duty cycle is low enough.