This is a circuit for amplifier circuit. But, this circuit has function for biasing the amplifier in temperature system. This circuit is based on LM114. This is the figure of the circuit;
In the circuit, a differential amplifier with the current source biased by an LM113. Since the LM113 supplies a reference voltage equal to the energy band gap of silicon, the output current of the 2N2222 will vary as absolute temperature. This compensates the temperature sensitivity of the trans-conductance of the differential amplifier making the gain temperature stable. Further, the operating current is regulated against supply variations keeping the gain stable over a wide supply range. As shown, the gain will change less than two per cent over a b55§C to a125§C temperature range. Using the LM114A monolithic transistor and low drift metal film resistors, the amplifier will have less than 2 mV/§C voltage drift. Even lower drift may be obtained by unbalancing the collector load resistors to null out the initial offset. Drift under nulled condition will be typically less than 0.5 mV/§C.
[Schematic circuit source: National Semiconductor Notes]
In the circuit, a differential amplifier with the current source biased by an LM113. Since the LM113 supplies a reference voltage equal to the energy band gap of silicon, the output current of the 2N2222 will vary as absolute temperature. This compensates the temperature sensitivity of the trans-conductance of the differential amplifier making the gain temperature stable. Further, the operating current is regulated against supply variations keeping the gain stable over a wide supply range. As shown, the gain will change less than two per cent over a b55§C to a125§C temperature range. Using the LM114A monolithic transistor and low drift metal film resistors, the amplifier will have less than 2 mV/§C voltage drift. Even lower drift may be obtained by unbalancing the collector load resistors to null out the initial offset. Drift under nulled condition will be typically less than 0.5 mV/§C.
[Schematic circuit source: National Semiconductor Notes]
0 comments:
Post a Comment