the DC gain requirement of opamp in PTAT

[lhlbluesky]

as we know, an opamp is usually used in PTAT circuit, and its DC gain should be large; but what is the DC gain requirement? how to determine the value of DC gain, and how much is enough? can anyone give me an explanation?thanks.

 

[girih192002]

Voltage Gain need to be high. it should be around 80 to 70 dB. We need the high gain because it will amplify the error voltage between two arms or node. opamp require to maintain same bias voltage at each arm or node which will reduce voltage mismatch thereby current mismatch in both which may affect the band gap voltage. you can either use five pack Diff amp (OTA) as amplifier..