help me to analyze the bandgap circuit

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liucheng311

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hi guys
i am analyzing this bandgap circuit,i want to know whether this bandgap topology is popular,and what is the andvantage and disadvantage of this circuit.
 

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delta_Vbe=Vbe1-Vbe2. This voltage is voltage drop on the resistor connected between two bipolars. So its current will be delta_Vbe/R. The PMOS current mirror will keep the current of NPN1 equal to the current of NPN2. The summing current will flow thru R2 (the resistor connected to ground). So Vref=vbe1+K.delta_Vbe. With suitable K, bandgap voltage can be achieved.
 
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thank you,leo_o2,it is nice to meet a compatriot on an foreign forum
i already know what you said,i wonder whether this topology is popular,since i meet this circuit for the first time.
and i have another question to ask you:
how high should i set for the opamp if i use an opamp to force the two node to be equal?i was told to set 60dB for the opmap(because high gain opamp is hard to be stable) ,but the simulation shows that there would be about 4mV difference between the two node,i want to know how bad is that since delta vbe is only tens of mV?
 

Basically, it is similar to the famous Brokaw bandgap in principle.
Nowadays, there are many other bandgap structures thru years' development according to special applications.
Gain depends on your accurate requirement. The higher gain is, the smaller difference it can achieve.
Generally, 4mV is still too big.
 
thank you!:-D
do you work in o2?well ,you really have much spare time,no offense:smile:
 

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