Datasheet LT1672, LT1673, LT1674 (Analog Devices) - 8

LT1672/LT1673/LT1674
W U TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Response Small-Signal Response Large-Signal Response
V 1672/3/4 G19 1672/3/4 G20 1672/3/4 G21 S = ±15V VS = 5V VS = 5V CL = 100pF CL = 100pF CL = 100pF AV = 5 AV = 5 AV = 5
U U W U APPLICATIO S I FOR ATIO Start-Up Characteristics
V+ V+ V+ Micropower op amps are sometimes not micropower during start-up, wreaking havoc on low current supplies. + + + In the worst case, there may not be enough supply current available to take the system up to nominal voltages. Figure – – – 1 is a graph of LT1673 supply current vs supply voltage 820k for the three limit cases of input offset that could occur V– V– 200k V– during start-up. The circuits are shown in Figure 2. One 16/2/3/4 F02 OUTPUT HIGH OUTPUT LOW OUTPUT AT VS/2 circuit creates a positive offset, forcing the output to come
Figure 2. Circuits for Start-Up Characteristics
up saturated high. Another circuit creates a negative offset, forcing the output to come up saturated low, while
Reverse Battery
the last brings up the output at half supply. In all cases, the The LT1672/LT1673/LT1674 are protected against reverse supply current is well behaved. Supply current is highest battery voltages up to 18V. In the event a reverse battery with the output forced high, so if one amplifier is unused, condition occurs, the supply current is typically less than it is best to force the output low or at half supply. 100nA (inputs grounded and outputs open). For typical 5 single supply applications with ground referred loads and µA) feedback networks, no other precautions are required. If 4 the reverse battery condition results in a negative voltage OUTPUT HIGH at either the input pins or output pin, the current into the 3 pin should be limited by an external resistor to less than 10mA. 2 OUTPUT LOW OUTPUT VS/2
Inputs
1 SUPPLY CURRENT PER AMPLIFIER ( While the LT1672/LT1673/LT1674 will function normally 0 with its inputs taken above the positive supply, the com- 0 1 2 3 4 5 TOTAL SUPPLY VOLTAGE (V) mon mode range does not extend beyond approximately 1672/3/4 FO1 300mV below the negative supply at room temperature.
Figure 1. Start-Up Characteristics
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