Low power 2 voltage references with 1 bandgap

[Fabien]

Hi all,

I want to design a low power bandgap reference. I made this kind of design:



but as it should be low power, the resistors should be very high as the low power OpAmp can't feed high current.

Anyway, it should be low power, but also have a good PSRR! I need 2 Vref, for example 1.23 and 1.2 in order to have 30mV of reference. So if the two have bad PSRR, the difference may could have good PSRR.

So I'm just wondering if there is any kind of circuit that can produce 2 voltages with 1 bandgap reference and low power. So resistors based bg ref should be avoided.

Thank you to let me know if there is any references, papers, books...

Fabien

 

[erikl]

Generate the 2^nd Vref with the help of a 2^nd low power OpAmp.

 

[Fabien]

So you mean with the same kind of design, and probably a second resistor?

 

[erikl]

Generate the 2^nd Vref from the 1^st Vref by using an OpAmp with feedback to set the correct gain. Usually you need 2 resistors to set the gain ;-)

 

[dick_freebird]

Even a low power op amp can drive a resistor load, if
you give it a source follower and have the headroom.
But of course then the -assembly- is not especially
low power. With enough ladder granularity you could get
the voltages you want right off the ladder (if all loading
is quiet and high-Z) or you could rebuffer with op amps.
But untrimmed unchopped CMOS op amps are liable to
add significant error / scatter to the references while
the ladder itself is going to be pretty predictable there.