how can i generate 2.5Volt output voltage with BandGap?

[lotoy]

200410cicc_vrefdesign

Hi all,
I wanna get a 2.5Volt output with a power supply of 3.3Volt. Because i give a cascode as the output stage of buffer, the combination of Amp and 2 resistors can not be used (because of the saturation requirement of cascode and power supply variation 2.7~3.3V).
Is there any other way to get 2.5V output?
Thanks in advance!!

Jian

 

[gevy]

You can use R-divider in bandgap voltage reference circuit without additional amplifier.

 

[huojinsi]

As the gevy'post, u can directly use resistor divider to form 2.5V refernece. At the output stage, use a follower constructed by a common drain amplifer instead of your cascode.
Hope it help u!

 

[DenisMark]

Follow reference u can find some examples sub 1V bgr ckts (with R divider too).
See 200410CICC_Vrefdesign.pdf, with ckts from chapter II it's easy to implement 2.5V reference output ever with 2.7V supply.

P.S.: If u add 2 resistors in series with drains of M1,M2 u can make Vds of M1,M2.M3 equal thus u obtain better current matching in current mirror.

 

[lotoy]

Thank you very much!
I do it in your way ,but PSRR is degraded, about 40dB. This is the main reason that i don't use this construction.

As the gevy'post, u can directly use resistor divider to form 2.5V refernece. At the output stage, use a follower constructed by a common drain amplifer instead of your cascode.
Hope it help u!

 

[maharshi_qis]

change emitter ares and resistor values...

 

[suria3]

You may generate a 1.2V as first voltage reference (conventional bandgap design) and then feed in 1.2V into a resistive feedback opamp to form a 2.5V. The matching of resistors are very important.

 

[cadenceucy]

Use this topology for circuit . Choose a simple op amp and then play with W/L to get your specifications