LM139/LM239/LM339/LM2901/LM3302 Low Power Low Offset ...

More documents

Recommendations

Info

LM139/LM239/LM339/LM2901/LM3302Typical Performance Characteristics LM139/LM239/LM339, LM139A/LM239A/LM339A, LM3302Supply CurrentInput CurrentOutput Saturation VoltageDS005706-34DS005706-35DS005706-36Response Time for VariousInput Overdrives — NegativeTransitionResponse Time for VariousInput Overdrives — PositiveTransitionDS005706-37DS005706-38Typical Performance Characteristics LM2901Supply CurrentInput CurrentOutput Saturation VoltageDS005706-39DS005706-40DS005706-41www.national.com 6
Typical Performance Characteristics LM2901 (Continued)Response Time for VariousInput Overdrives — NegativeTransitionResponse Time for VariousInput Overdrives-PositiveTransitionLM139/LM239/LM339/LM2901/LM3302Application HintsDS005706-42The LM139 series are high gain, wide bandwidth deviceswhich, like most comparators, can easily oscillate if the outputlead is inadvertently allowed to capacitively couple to theinputs via stray capacitance. This shows up only during theoutput voltage transition intervals as the comparatorchanges states. Power supply bypassing is not required tosolve this problem. Standard PC board layout is helpful as itreduces stray input-output coupling. Reducing this input resistorsto < 10 kΩ reduces the feedback signal levels and finally,adding even a small amount (1 to 10 mV) of positivefeedback (hysteresis) causes such a rapid transition that oscillationsdue to stray feedback are not possible. Simplysocketing the IC and attaching resistors to the pins will causeinput-output oscillations during the small transition intervalsunless hysteresis is used. If the input signal is a pulse waveform,with relatively fast rise and fall times, hysteresis is notrequired.All pins of any unused comparators should be tied to thenegative supply.The bias network of the LM139 series establishes a draincurrent which is independent of the magnitude of the powersupply voltage over the range of from 2 V DC to 30 V DC .It is usually unnecessary to use a bypass capacitor acrossthe power supply line.DS005706-43The differential input voltage may be larger than V + withoutdamaging the device. Protection should be provided to preventthe input voltages from going negative more than −0.3V DC (at 25˚C). An input clamp diode can be used as shownin the applications section.The output of the LM139 series is the uncommitted collectorof a grounded-emitter NPN output transistor. Many collectorscan be tied together to provide an output OR’ing function. Anoutput pull-up resistor can be connected to any availablepower supply voltage within the permitted supply voltagerange and there is no restriction on this voltage due to themagnitude of the voltage which is applied to the V + terminalof the LM139A package. The output can also be used as asimple SPST switch to ground (when a pull-up resistor is notused). The amount of current which the output device cansink is limited by the drive available (which is independent ofV + ) and the β of this device. When the maximum current limitis reached (approximately 16 mA), the output transistor willcome out of saturation and the output voltage will rise veryrapidly. The output saturation voltage is limited by the approximately60Ω R SAT of the output transistor. The low offsetvoltage of the output transistor (1 mV) allows the output toclamp essentially to ground level for small load currents.Typical Applications (V + = 5.0 V DC )Basic ComparatorDriving CMOSDriving TTLDS005706-3DS005706-4DS005706-57www.national.com
Page 1: LM139/LM239/LM339/LM2901/LM3302Low
Page 9 and 10: Typical Applications (V + = 15 V DC
Page 17: Split-Supply Applications (V + =+15
Page 20: LM139/LM239/LM339/LM2901/LM3302 Low

LM139/LM239/LM339/LM2901/LM3302 Low Power Low Offset ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?