Is the Bandgap output voltage dependant on the BJT model ?

[aryajur]

Bandgap circuit voltage

Hello,
I am trying to simulate a bandgap circuit. When I do a DC Analysis temperature sweep in Spectre, I see the variation in Vout from around 716mV to 700mV. If I use another BJT diode model the voltage level falls to around 600mV, but the current consumption of the whole circuit increase !
I don't understand this. Is the Bandgap output voltage dependant on the BJT model we use? Or do we have control over it and can be adjusted by changing parameters of circuit components?

 

[blue_orangee]

Bandgap circuit voltage

I wonder it too.The typical bandgap voltage reference is about 1.205 or a little more.Why the voltage does not fit?

 

[aryajur]

Re: Bandgap circuit voltage

Actually I am making a subbandgap reference source which generates half the normal bandgap voltage. But still, does it only depend on the BJT model we use???

 

[aryajur]

Re: Bandgap circuit voltage

I discovered that it can be adjusted by changing circuit parameters. It mainly depends on the amount of current we pass through the Diodes in our circuit

 

[jake]

Bandgap circuit voltage

Does anyone know how to realize a 1.6v output bandgap? And when I simulate the OPA of the bandgap, the gain is minus. What's happen ? The transistors are worked in desired regions.

 

[steer]

Re: Bandgap circuit voltage

Does anyone know how to realize a 1.6v output bandgap?

Quite easy. Just use GaAs instead of Si. Everything else leave unchanged.

 

[qutang]

Bandgap circuit voltage

I think the model is important .the lose current is too large.

 

[jake]

Bandgap circuit voltage

steer,
you say that"Quite easy. Just use GaAs instead of Si. Everything else leave unchanged. "
But I must use TSMC 0.18 PROCESS, it can't use GaAs, really ? Someone tell me that I can use a buffer with a resistor divider to realize a 1.6v output voltage. But I don't know how to do it.

 

[j2005]

Re: Bandgap circuit voltage

Changing the size of the BJT doesn't do much to the current. Try changing the resistors instead.

 

[cliffj]

Re: Bandgap circuit voltage

Dear Jack,

since you already have a stable bg voltage around 1.2V. You just need a
buffer and PMOS/NMOS output stage , two resistors. Then you can get any voltage by adjusting the resistor ration. Ilike a regulator)

 

[rambus_ddr]

Re: Bandgap circuit voltage

Hi,Jake
It's easy to realize to use a opamp(which maybe the bandgap error opamp) and two resistors, the voltage can get Vref(R1+ R2)/R1.

Hi,aryajur
when you use another BJT model, the Is is changed, so the Vbe changed even though your Ic current keep not changed, because the Vbe=VTln(Ic/Is).