Difference between LDO and opamp

[calculus_cuthbert]

Hi,

I have some basic questions regarding LDO and opamp based amplifiers:

1. When is a LDO used and why can't an opamp based amplifier be used? For e.g. I came across a sensor analog front end system. A bandgap was designed to generate a reference voltage of ~1.2V. But the ADC needed a 2.4V reference so a LDO was designed with the bandgap as its reference. My question is: Why was a LDO designed and not a non-inverting/inverting opamp amplifier?

2. In the same sensor analog front end, another reference was designed for the digital blocks. The reference was ~1.2V. Here also, a LDO was designed with the bandgap as it's reference. My question is why wasn't a buffer opamp used instead?

Could someone please help me understand why?

Thanks!!

 

[crutschow]

1. The LDO was probably simpler and used less chip space then an op amp.

2. See answer to 1.